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<li class="toctree-l2"><a class="reference internal" href="#migrating-from-web3-to-ethers-v4">Migrating from Web3 to ethers v4</a></li>
<li class="toctree-l2"><a class="reference internal" href="#migrating-from-ethers-v3-to-ethers-v4">Migrating from ethers v3 to ethers v4</a><ul>
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<div class="section" id="migration-guides">
<span id="migration"></span><h1>Migration Guides<a class="headerlink" href="#migration-guides" title="Permalink to this headline"></a></h1>
<div class="section" id="migrating-from-web3-to-ethers-v4">
<h2>Migrating from Web3 to ethers v4<a class="headerlink" href="#migrating-from-web3-to-ethers-v4" title="Permalink to this headline"></a></h2>
<p>Todo: This is coming soon.</p>
</div>
<hr class="docutils" />
<div class="section" id="migrating-from-ethers-v3-to-ethers-v4">
<h2>Migrating from ethers v3 to ethers v4<a class="headerlink" href="#migrating-from-ethers-v3-to-ethers-v4" title="Permalink to this headline"></a></h2>
<p>A lot of the functionality has remained the same, but there has been some
slight refactoring and improved paradigms.</p>
<hr class="docutils" />
<div class="section" id="constants">
<h3>Constants<a class="headerlink" href="#constants" title="Permalink to this headline"></a></h3>
<p>All constants have moved from the utils to the root ethers object.</p>
<div class="literal-block-wrapper docutils container" id="id1">
<div class="code-block-caption"><span class="caption-text"><em>Constants — ethers v3</em></span><a class="headerlink" href="#id1" title="Permalink to this code"></a></div>
<div class="highlight-javascript notranslate"><div class="highlight"><pre><span></span><span class="kd">let</span> <span class="nx">one</span> <span class="o">=</span> <span class="nx">ethers</span><span class="p">.</span><span class="nx">utils</span><span class="p">.</span><span class="nx">constants</span><span class="p">.</span><span class="nx">One</span><span class="p">;</span>
</pre></div>
</div>
</div>
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<div class="code-block-caption"><span class="caption-text"><em>Constants — ethers v4</em></span><a class="headerlink" href="#id2" title="Permalink to this code"></a></div>
<div class="highlight-javascript notranslate"><div class="highlight"><pre><span></span><span class="kd">let</span> <span class="nx">one</span> <span class="o">=</span> <span class="nx">ethers</span><span class="p">.</span><span class="nx">constants</span><span class="p">.</span><span class="nx">One</span><span class="p">;</span>
</pre></div>
</div>
</div>
</div>
<hr class="docutils" />
<div class="section" id="deploying-contracts">
<h3>Deploying Contracts<a class="headerlink" href="#deploying-contracts" title="Permalink to this headline"></a></h3>
<p>Deploying contracts has undergone some significant change. The new API is more
seamless and reduces the amount of low-level understanding that is required,
such as the details of how <em>init transaction</em> behave.</p>
<p>More complex and complete objects are also returned through-out the
process, so there are far less calls to utility functions after a deployment
required to populate databases and track status.</p>
<div class="literal-block-wrapper docutils container" id="id3">
<div class="code-block-caption"><span class="caption-text"><em>ethers v3</em></span><a class="headerlink" href="#id3" title="Permalink to this code"></a></div>
<div class="highlight-javascript notranslate"><div class="highlight"><pre><span></span><span class="kd">let</span> <span class="nx">tx</span> <span class="o">=</span> <span class="nx">Contract</span><span class="p">.</span><span class="nx">getDeployTransaction</span><span class="p">(</span><span class="nx">bytecode</span><span class="p">,</span> <span class="nx">abi</span><span class="p">,</span> <span class="nx">arg1</span><span class="p">,</span> <span class="nx">arg2</span><span class="p">);</span>
<span class="c1">// overrides</span>
<span class="nx">tx</span><span class="p">.</span><span class="nx">gasLimit</span> <span class="o">=</span> <span class="mi">1500000</span><span class="p">;</span>
<span class="nx">wallet</span><span class="p">.</span><span class="nx">sendTransaction</span><span class="p">(</span><span class="nx">tx</span><span class="p">).</span><span class="nx">then</span><span class="p">((</span><span class="nx">tx</span><span class="p">)</span> <span class="p">=&gt;</span> <span class="p">{</span>
<span class="kd">let</span> <span class="nx">contractAddress</span> <span class="o">=</span> <span class="nx">ethers</span><span class="p">.</span><span class="nx">utils</span><span class="p">.</span><span class="nx">getContractAddress</span><span class="p">(</span><span class="nx">tx</span><span class="p">);</span>
<span class="kd">let</span> <span class="nx">contract</span> <span class="o">=</span> <span class="k">new</span> <span class="nx">ethers</span><span class="p">.</span><span class="nx">Contract</span><span class="p">(</span><span class="nx">contractAddress</span><span class="p">,</span> <span class="nx">abi</span><span class="p">,</span> <span class="nx">wallet</span><span class="p">);</span>
<span class="nx">provider</span><span class="p">.</span><span class="nx">waitForTransaction</span><span class="p">(</span><span class="nx">tx</span><span class="p">).</span><span class="nx">then</span><span class="p">((</span><span class="nx">tx</span><span class="p">)</span> <span class="p">=&gt;</span> <span class="p">{</span>
<span class="nx">provider</span><span class="p">.</span><span class="nx">getTransactionReceipt</span><span class="p">(</span><span class="nx">tx</span><span class="p">.</span><span class="nx">hash</span><span class="p">).</span><span class="nx">then</span><span class="p">((</span><span class="nx">receipt</span><span class="p">)</span> <span class="p">=&gt;</span> <span class="p">{</span>
<span class="k">if</span> <span class="p">(</span><span class="nx">receipt</span><span class="p">.</span><span class="nx">status</span> <span class="o">===</span> <span class="mi">0</span><span class="p">)</span> <span class="p">{</span>
<span class="k">throw</span> <span class="k">new</span> <span class="nb">Error</span><span class="p">(</span><span class="s1">&#39;failed to deploy&#39;</span><span class="p">);</span>
<span class="p">}</span>
<span class="nx">contract</span><span class="p">.</span><span class="nx">someFunction</span><span class="p">();</span>
<span class="p">});</span>
<span class="p">});</span>
<span class="p">});</span>
</pre></div>
</div>
</div>
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<div class="code-block-caption"><span class="caption-text"><em>Deploy a Contract — ethers v4</em></span><a class="headerlink" href="#id4" title="Permalink to this code"></a></div>
<div class="highlight-javascript notranslate"><div class="highlight"><pre><span></span><span class="c1">// Construct a Contract Factory</span>
<span class="kd">let</span> <span class="nx">factory</span> <span class="o">=</span> <span class="k">new</span> <span class="nx">ethers</span><span class="p">.</span><span class="nx">ContractFactory</span><span class="p">(</span><span class="nx">abi</span><span class="p">,</span> <span class="nx">bytecode</span><span class="p">,</span> <span class="nx">signer</span><span class="p">);</span>
<span class="c1">// Deploy automatically detects gasLimit and all other parameters</span>
<span class="c1">// Overrides can optionally be passed as an extra parameter</span>
<span class="c1">// Optional; all unspecified values will queried from the network</span>
<span class="kd">let</span> <span class="nx">overrides</span> <span class="o">=</span> <span class="p">{</span> <span class="p">};</span>
<span class="nx">factory</span><span class="p">.</span><span class="nx">deploy</span><span class="p">(</span><span class="nx">arg1</span><span class="p">,</span> <span class="nx">arg2</span><span class="p">,</span> <span class="nx">overrides</span><span class="p">).</span><span class="nx">then</span><span class="p">((</span><span class="nx">contract</span><span class="p">)</span> <span class="p">=&gt;</span> <span class="p">{</span>
<span class="c1">// The contract is returned immediately; it has not been mined yet</span>
<span class="c1">// The contract known its address (before it is even mined)</span>
<span class="nx">console</span><span class="p">.</span><span class="nx">log</span><span class="p">(</span><span class="nx">contract</span><span class="p">.</span><span class="nx">address</span><span class="p">);</span>
<span class="c1">// You can access the in-flight transaction that is currently waiting to be mined</span>
<span class="nx">console</span><span class="p">.</span><span class="nx">log</span><span class="p">(</span><span class="nx">contract</span><span class="p">.</span><span class="nx">deployTransaction</span><span class="p">);</span>
<span class="c1">// A full transaction with:</span>
<span class="c1">// - from</span>
<span class="c1">// - nonce</span>
<span class="c1">// - hash</span>
<span class="c1">// - all other Transaction Response fields</span>
<span class="c1">// - wait() =&gt; Promise that resolves to the TransactionReceipt</span>
<span class="c1">// The &quot;deployed()&quot; function will return a Promise that resolves</span>
<span class="c1">// to the contract, once it has been mined. If the contract fails</span>
<span class="c1">// to deploy, the Promise will reject.</span>
<span class="nx">contract</span><span class="p">.</span><span class="nx">deployed</span><span class="p">().</span><span class="nx">then</span><span class="p">((</span><span class="nx">contract</span><span class="p">)</span> <span class="p">=&gt;</span> <span class="p">{</span>
<span class="c1">// The contract is now deployed</span>
<span class="nx">contract</span><span class="p">.</span><span class="nx">someFunction</span><span class="p">();</span>
<span class="p">},</span> <span class="p">(</span><span class="nx">error</span><span class="p">)</span> <span class="p">=&gt;</span> <span class="p">{</span>
<span class="c1">// The transaction failed to deploy</span>
<span class="nx">console</span><span class="p">.</span><span class="nx">log</span><span class="p">(</span><span class="s1">&#39;Failed to deploy in TX:&#39;</span><span class="p">,</span> <span class="nx">error</span><span class="p">.</span><span class="nx">transactionHash</span><span class="p">);</span>
<span class="p">});</span>
<span class="p">});</span>
</pre></div>
</div>
</div>
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<div class="code-block-caption"><span class="caption-text"><em>Deploy a Contract with async/await — ethers v4</em></span><a class="headerlink" href="#id5" title="Permalink to this code"></a></div>
<div class="highlight-javascript notranslate"><div class="highlight"><pre><span></span><span class="nx">async</span> <span class="kd">function</span><span class="p">()</span> <span class="p">{</span>
<span class="kd">let</span> <span class="nx">factory</span> <span class="o">=</span> <span class="k">new</span> <span class="nx">ethers</span><span class="p">.</span><span class="nx">ContractFactory</span><span class="p">(</span><span class="nx">abi</span><span class="p">,</span> <span class="nx">bytecode</span><span class="p">,</span> <span class="nx">signer</span><span class="p">);</span>
<span class="kd">let</span> <span class="nx">contract</span> <span class="o">=</span> <span class="nx">await</span> <span class="nx">factory</span><span class="p">.</span><span class="nx">deploy</span><span class="p">(</span><span class="nx">arg1</span><span class="p">,</span> <span class="nx">arg2</span><span class="p">);</span>
<span class="k">try</span> <span class="p">{</span>
<span class="nx">await</span> <span class="nx">contract</span><span class="p">.</span><span class="nx">deployed</span><span class="p">();</span>
<span class="p">}</span> <span class="k">catch</span> <span class="p">(</span><span class="nx">error</span><span class="p">)</span> <span class="p">{</span>
<span class="nx">console</span><span class="p">.</span><span class="nx">log</span><span class="p">(</span><span class="s1">&#39;Failed to deploy in TX:&#39;</span><span class="p">,</span> <span class="nx">error</span><span class="p">.</span><span class="nx">transactionHash</span><span class="p">);</span>
<span class="k">throw</span> <span class="nx">error</span><span class="p">;</span>
<span class="p">}</span>
<span class="nx">contract</span><span class="p">.</span><span class="nx">someFunction</span><span class="p">();</span>
<span class="p">}</span>
</pre></div>
</div>
</div>
<div class="literal-block-wrapper docutils container" id="id6">
<div class="code-block-caption"><span class="caption-text"><em>Get Deployment Transaction — ethers v4</em></span><a class="headerlink" href="#id6" title="Permalink to this code"></a></div>
<div class="highlight-javascript notranslate"><div class="highlight"><pre><span></span><span class="c1">// If you still need the deployment transaction, and don&#39;t wish to</span>
<span class="c1">// actually deploy, you can much more easily just use the Interface</span>
<span class="c1">// object without the need for a provider or signer.</span>
<span class="kd">let</span> <span class="nx">factory</span> <span class="o">=</span> <span class="k">new</span> <span class="nx">ethers</span><span class="p">.</span><span class="nx">ContractFactory</span><span class="p">(</span><span class="nx">abi</span><span class="p">,</span> <span class="nx">bytecode</span><span class="p">);</span>
<span class="kd">let</span> <span class="nx">tx</span> <span class="o">=</span> <span class="nx">factory</span><span class="p">.</span><span class="nx">getDeployTransaction</span><span class="p">(</span><span class="nx">arg1</span><span class="p">,</span> <span class="nx">arg2</span><span class="p">);</span>
</pre></div>
</div>
</div>
</div>
<hr class="docutils" />
<div class="section" id="encrypted-wallets">
<h3>Encrypted Wallets<a class="headerlink" href="#encrypted-wallets" title="Permalink to this headline"></a></h3>
<div class="literal-block-wrapper docutils container" id="id7">
<div class="code-block-caption"><span class="caption-text"><em>Checking JSON Wallets — ethers v3</em></span><a class="headerlink" href="#id7" title="Permalink to this code"></a></div>
<div class="highlight-javascript notranslate"><div class="highlight"><pre><span></span><span class="kd">let</span> <span class="nx">isJsonWallet</span> <span class="o">=</span> <span class="nx">ethers</span><span class="p">.</span><span class="nx">Wallet</span><span class="p">.</span><span class="nx">isEncryptedWallet</span><span class="p">(</span><span class="nx">json</span><span class="p">);</span>
</pre></div>
</div>
</div>
<div class="literal-block-wrapper docutils container" id="id8">
<div class="code-block-caption"><span class="caption-text"><em>Checking JSON Wallets — ethers v4</em></span><a class="headerlink" href="#id8" title="Permalink to this code"></a></div>
<div class="highlight-javascript notranslate"><div class="highlight"><pre><span></span><span class="kd">let</span> <span class="nx">address</span> <span class="o">=</span> <span class="nx">ethers</span><span class="p">.</span><span class="nx">utils</span><span class="p">.</span><span class="nx">getJsonWalletAddress</span><span class="p">(</span><span class="nx">json</span><span class="p">);</span>
<span class="kd">let</span> <span class="nx">isJsonWallet</span> <span class="o">=</span> <span class="p">(</span><span class="nx">address</span> <span class="o">!==</span> <span class="kc">null</span><span class="p">)</span>
</pre></div>
</div>
</div>
<div class="literal-block-wrapper docutils container" id="id9">
<div class="code-block-caption"><span class="caption-text"><em>Decrypting JSON Wallets — ethers v3</em></span><a class="headerlink" href="#id9" title="Permalink to this code"></a></div>
<div class="highlight-javascript notranslate"><div class="highlight"><pre><span></span><span class="kd">let</span> <span class="nx">wallet</span> <span class="o">=</span> <span class="nx">await</span> <span class="nx">ethers</span><span class="p">.</span><span class="nx">Wallet</span><span class="p">.</span><span class="nx">fromEncryptedWallet</span><span class="p">(</span><span class="nx">json</span><span class="p">,</span> <span class="nx">password</span><span class="p">);</span>
</pre></div>
</div>
</div>
<div class="literal-block-wrapper docutils container" id="id10">
<div class="code-block-caption"><span class="caption-text"><em>Decrypting JSON Wallets — ethers v4</em></span><a class="headerlink" href="#id10" title="Permalink to this code"></a></div>
<div class="highlight-javascript notranslate"><div class="highlight"><pre><span></span><span class="kd">let</span> <span class="nx">wallet</span> <span class="o">=</span> <span class="nx">await</span> <span class="nx">ethers</span><span class="p">.</span><span class="nx">Wallet</span><span class="p">.</span><span class="nx">fromEncryptedJson</span><span class="p">(</span><span class="nx">json</span><span class="p">,</span> <span class="nx">password</span><span class="p">);</span>
</pre></div>
</div>
</div>
</div>
<hr class="docutils" />
<div class="section" id="events">
<h3>Events<a class="headerlink" href="#events" title="Permalink to this headline"></a></h3>
<p>Events now behave like a modern JavaScript Event Emitter, rather than a 1995
web browser.</p>
<p>The events now play nicer with the arrow operator (i.e. <code class="docutils literal notranslate"><span class="pre">()</span> <span class="pre">=&gt;</span> <span class="pre">{</span> <span class="pre">...</span> <span class="pre">}</span></code>),
since rather than modifying the <cite>this</cite> inside the callbacks, an additional
rich object is passed along.</p>
<div class="literal-block-wrapper docutils container" id="id11">
<div class="code-block-caption"><span class="caption-text"><em>Events — ethers v3</em></span><a class="headerlink" href="#id11" title="Permalink to this code"></a></div>
<div class="highlight-javascript notranslate"><div class="highlight"><pre><span></span><span class="c1">// Solidity: event SomeEvent(address foo, uint256 bar)</span>
<span class="nx">contract</span><span class="p">.</span><span class="nx">onsomeevent</span> <span class="o">=</span> <span class="kd">function</span><span class="p">(</span><span class="nx">foo</span><span class="p">,</span> <span class="nx">bar</span><span class="p">)</span> <span class="p">{</span>
<span class="nx">console</span><span class="p">.</span><span class="nx">log</span><span class="p">(</span><span class="nx">foo</span><span class="p">,</span> <span class="nx">bar</span><span class="p">);</span>
<span class="c1">// The Log was available at this:</span>
<span class="c1">// - this.event</span>
<span class="c1">// - this.removeListener()</span>
<span class="p">};</span>
</pre></div>
</div>
</div>
<div class="literal-block-wrapper docutils container" id="id12">
<div class="code-block-caption"><span class="caption-text"><em>Listening to an Event — ethers v4</em></span><a class="headerlink" href="#id12" title="Permalink to this code"></a></div>
<div class="highlight-javascript notranslate"><div class="highlight"><pre><span></span><span class="c1">// Solidity: event SomeEvent(address foo, uint256 bar)</span>
<span class="nx">contract</span><span class="p">.</span><span class="nx">on</span><span class="p">(</span><span class="s1">&#39;SomeEvent&#39;</span><span class="p">,</span> <span class="p">(</span><span class="nx">foo</span><span class="p">,</span> <span class="nx">bar</span><span class="p">,</span> <span class="nx">eventInfo</span><span class="p">)</span> <span class="p">=&gt;</span> <span class="p">{</span>
<span class="nx">console</span><span class="p">.</span><span class="nx">log</span><span class="p">(</span><span class="nx">foo</span><span class="p">,</span> <span class="nx">bar</span><span class="p">);</span>
<span class="c1">// eventInfo</span>
<span class="c1">// - Log (blockNumber, blockHash, txHash, removed, address, data, etc.)</span>
<span class="c1">// - args: [ foo, bar ]</span>
<span class="c1">// - decode: (data, topics) =&gt; [ foo, bar ]</span>
<span class="c1">// - event: &quot;SomeEvent&quot;</span>
<span class="c1">// - eventSignature: &quot;SomeEvent(address,uint256)&quot;</span>
<span class="c1">// - removeListener: () =&gt; removes this listener</span>
<span class="c1">// - getBlock: () =&gt; returns a Promise of the block</span>
<span class="c1">// - getTransaction: () =&gt; returns a Promise of transaction</span>
<span class="c1">// - getTransactionReceipt: () =&gt; returns a Promise of the receipt</span>
<span class="p">});</span>
</pre></div>
</div>
</div>
<div class="literal-block-wrapper docutils container" id="id13">
<div class="code-block-caption"><span class="caption-text"><em>Indexed Events — ethers v3</em></span><a class="headerlink" href="#id13" title="Permalink to this code"></a></div>
<div class="highlight-javascript notranslate"><div class="highlight"><pre><span></span><span class="c1">// Detecting a parameters is an indexed hash, and not a value</span>
<span class="nx">contract</span><span class="p">.</span><span class="nx">someEvent</span> <span class="o">=</span> <span class="kd">function</span><span class="p">(</span><span class="nx">foo</span><span class="p">)</span> <span class="p">{</span>
<span class="k">if</span> <span class="p">(</span><span class="nx">foo</span><span class="p">.</span><span class="nx">indexed</span><span class="p">)</span> <span class="p">{</span>
<span class="c1">// The value is just a hash to filter by</span>
<span class="p">}</span>
<span class="p">}</span>
</pre></div>
</div>
</div>
<div class="literal-block-wrapper docutils container" id="id14">
<div class="code-block-caption"><span class="caption-text"><em>Indexed Events — ethers v4</em></span><a class="headerlink" href="#id14" title="Permalink to this code"></a></div>
<div class="highlight-javascript notranslate"><div class="highlight"><pre><span></span><span class="kd">let</span> <span class="nx">Indexed</span> <span class="o">=</span> <span class="nx">ethers</span><span class="p">.</span><span class="nx">types</span><span class="p">.</span><span class="nx">Indexed</span><span class="p">;</span>
<span class="c1">// Detecting a parameters is an indexed hash, and not a value</span>
<span class="nx">contract</span><span class="p">.</span><span class="nx">someEvent</span> <span class="o">=</span> <span class="kd">function</span><span class="p">(</span><span class="nx">foo</span><span class="p">)</span> <span class="p">{</span>
<span class="k">if</span> <span class="p">(</span><span class="nx">Indexed</span><span class="p">.</span><span class="nx">isIndexed</span><span class="p">(</span><span class="nx">foo</span><span class="p">))</span> <span class="p">{</span>
<span class="c1">// The value is just a hash to filter by</span>
<span class="p">}</span>
<span class="p">}</span>
</pre></div>
</div>
</div>
<div class="literal-block-wrapper docutils container" id="id15">
<div class="code-block-caption"><span class="caption-text"><em>Filtering Events — ethers v4</em></span><a class="headerlink" href="#id15" title="Permalink to this code"></a></div>
<div class="highlight-javascript notranslate"><div class="highlight"><pre><span></span><span class="c1">// Solidity: event SomeEvent(address indexed foo, uint256 bar)</span>
<span class="kd">let</span> <span class="nx">address</span> <span class="o">=</span> <span class="s1">&#39;0x8B40a2E27C5E87aa66DfA7F80BF675176F49DCA7&#39;</span><span class="p">;</span>
<span class="kd">let</span> <span class="nx">filter</span> <span class="o">=</span> <span class="nx">contract</span><span class="p">.</span><span class="nx">filters</span><span class="p">.</span><span class="nx">SomeEvent</span><span class="p">(</span><span class="nx">address</span><span class="p">,</span> <span class="kc">null</span><span class="p">);</span>
<span class="nx">console</span><span class="p">.</span><span class="nx">log</span><span class="p">(</span><span class="nx">filter</span><span class="p">);</span>
<span class="c1">// {</span>
<span class="c1">// address: contract.address,</span>
<span class="c1">// topics: [</span>
<span class="c1">// 0xdde371250dcd21c331edbb965b9163f4898566e8c60e28868533281edf66ab03,</span>
<span class="c1">// 0x0000000000000000000000008b40a2e27c5e87aa66dfa7f80bf675176f49dca7</span>
<span class="c1">// ]</span>
<span class="c1">// }</span>
<span class="nx">contract</span><span class="p">.</span><span class="nx">on</span><span class="p">(</span><span class="nx">filter</span><span class="p">,</span> <span class="p">(</span><span class="nx">foo</span><span class="p">,</span> <span class="nx">bar</span><span class="p">,</span> <span class="nx">eventInfo</span><span class="p">)</span> <span class="p">=&gt;</span> <span class="p">{</span>
<span class="nx">console</span><span class="p">.</span><span class="nx">log</span><span class="p">(</span><span class="nx">foo</span> <span class="o">===</span> <span class="nx">address</span><span class="p">);</span>
<span class="c1">// true</span>
<span class="p">});</span>
</pre></div>
</div>
</div>
<p>If there are multiple events with the same name:</p>
<div class="literal-block-wrapper docutils container" id="id16">
<div class="code-block-caption"><span class="caption-text"><em>Event Name Collision — ethers v4</em></span><a class="headerlink" href="#id16" title="Permalink to this code"></a></div>
<div class="highlight-javascript notranslate"><div class="highlight"><pre><span></span><span class="c1">// Solidity</span>
<span class="c1">// - event SomeEvent(address foo, uint256 bar)</span>
<span class="c1">// - event SomeEvent(address foo, address bar)</span>
<span class="nx">contract</span><span class="p">.</span><span class="nx">on</span><span class="p">(</span><span class="s1">&#39;SomeEvent(address, uint256)&#39;</span><span class="p">,</span> <span class="p">(</span><span class="nx">foo</span><span class="p">,</span> <span class="nx">bar</span><span class="p">,</span> <span class="nx">eventInfo</span><span class="p">)</span> <span class="p">=&gt;</span> <span class="p">{</span>
<span class="c1">// ...</span>
<span class="p">});</span>
<span class="nx">contract</span><span class="p">.</span><span class="nx">on</span><span class="p">(</span><span class="s1">&#39;SomeEvent(address, address)&#39;</span><span class="p">,</span> <span class="p">(</span><span class="nx">foo</span><span class="p">,</span> <span class="nx">bar</span><span class="p">,</span> <span class="nx">eventInfo</span><span class="p">)</span> <span class="p">=&gt;</span> <span class="p">{</span>
<span class="c1">// ...</span>
<span class="p">});</span>
</pre></div>
</div>
</div>
</div>
<hr class="docutils" />
<div class="section" id="fetching-json">
<h3>Fetching JSON<a class="headerlink" href="#fetching-json" title="Permalink to this headline"></a></h3>
<p>The JSON fetching routine, since it was mostly used for Providers was
on the Provider object in v3. In v4, it has moved to utils, since there
are other common cases where it may be useful.</p>
<div class="literal-block-wrapper docutils container" id="id17">
<div class="code-block-caption"><span class="caption-text"><em>Fetching JSON — ethers v3</em></span><a class="headerlink" href="#id17" title="Permalink to this code"></a></div>
<div class="highlight-javascript notranslate"><div class="highlight"><pre><span></span><span class="nx">ethers</span><span class="p">.</span><span class="nx">providers</span><span class="p">.</span><span class="nx">Provider</span><span class="p">.</span><span class="nx">fetchJson</span><span class="p">(</span><span class="nx">url</span><span class="p">).</span><span class="nx">then</span><span class="p">((</span><span class="nx">object</span><span class="p">)</span> <span class="p">=&gt;</span> <span class="p">{</span>
<span class="c1">// ...</span>
<span class="p">});</span>
</pre></div>
</div>
</div>
<div class="literal-block-wrapper docutils container" id="id18">
<div class="code-block-caption"><span class="caption-text"><em>Fetching JSON — ethers v4</em></span><a class="headerlink" href="#id18" title="Permalink to this code"></a></div>
<div class="highlight-javascript notranslate"><div class="highlight"><pre><span></span><span class="nx">ethers</span><span class="p">.</span><span class="nx">utils</span><span class="p">.</span><span class="nx">fetchJson</span><span class="p">(</span><span class="nx">url</span><span class="p">).</span><span class="nx">then</span><span class="p">((</span><span class="nx">object</span><span class="p">)</span> <span class="p">=&gt;</span> <span class="p">{</span>
<span class="c1">// ...</span>
<span class="p">});</span>
</pre></div>
</div>
</div>
</div>
<hr class="docutils" />
<div class="section" id="interfaces">
<h3>Interfaces<a class="headerlink" href="#interfaces" title="Permalink to this headline"></a></h3>
<p>This has always been a fairly low-level API, and mostly available for
framework developers and other tools that require quite specific access
to working with an ABI. Most of the changes are to simplify the interaction,
so while there will probably be changes required, if you use this class, the
complexity and size of your code should be reduced.</p>
<div class="literal-block-wrapper docutils container" id="id19">
<div class="code-block-caption"><span class="caption-text"><em>Interface — ethers v3</em></span><a class="headerlink" href="#id19" title="Permalink to this code"></a></div>
<div class="highlight-javascript notranslate"><div class="highlight"><pre><span></span><span class="kd">let</span> <span class="nx">iface</span> <span class="o">=</span> <span class="nx">ethers</span><span class="p">.</span><span class="nx">Interface</span><span class="p">(</span><span class="nx">address</span><span class="p">,</span> <span class="nx">abi</span><span class="p">,</span> <span class="nx">providerOrSigner</span><span class="p">);</span>
</pre></div>
</div>
</div>
<div class="literal-block-wrapper docutils container" id="id20">
<div class="code-block-caption"><span class="caption-text"><em>Interface — ethers v4</em></span><a class="headerlink" href="#id20" title="Permalink to this code"></a></div>
<div class="highlight-javascript notranslate"><div class="highlight"><pre><span></span><span class="kd">let</span> <span class="nx">iface</span> <span class="o">=</span> <span class="nx">ethers</span><span class="p">.</span><span class="nx">utils</span><span class="p">.</span><span class="nx">Interface</span><span class="p">(</span><span class="nx">address</span><span class="p">,</span> <span class="nx">abi</span><span class="p">,</span> <span class="nx">providerOrSigner</span><span class="p">);</span>
</pre></div>
</div>
</div>
<div class="literal-block-wrapper docutils container" id="id21">
<div class="code-block-caption"><span class="caption-text"><em>Function Description — ethers v3</em></span><a class="headerlink" href="#id21" title="Permalink to this code"></a></div>
<div class="highlight-javascript notranslate"><div class="highlight"><pre><span></span><span class="kd">let</span> <span class="nx">address</span> <span class="o">=</span> <span class="s2">&quot;0x8B40a2E27C5E87aa66DfA7F80BF675176F49DCA7&quot;</span><span class="p">;</span>
<span class="kd">let</span> <span class="nx">value</span> <span class="o">=</span> <span class="mi">1000</span><span class="p">;</span>
<span class="c1">// Solidity: function someFunc(address foo, uint256 bar) constant returns (address result)</span>
<span class="kd">let</span> <span class="nx">functionCallable</span> <span class="o">=</span> <span class="nx">iface</span><span class="p">.</span><span class="nx">functionst</span><span class="p">.</span><span class="nx">someFunc</span>
<span class="c1">// functionInfo</span>
<span class="c1">// - inputs: { names: [ &quot;foo&quot;, &quot;bar&quot; ], types: [ &quot;address&quot;, &quot;uint256&quot; ] }</span>
<span class="c1">// - outputs: { names: [ &quot;result&quot; ], types: [ &quot;address&quot; ] }</span>
<span class="c1">// - payable: false</span>
<span class="c1">// - parseResult: (data) =&gt; any</span>
<span class="c1">// - signature: &quot;someFunc(address,uint256)&quot;</span>
<span class="c1">// - sighash: &quot;0xd90a6a67&quot;</span>
<span class="kd">let</span> <span class="nx">data</span> <span class="o">=</span> <span class="nx">functionCallable</span><span class="p">(</span><span class="nx">address</span><span class="p">,</span> <span class="nx">value</span><span class="p">);</span>
<span class="kd">let</span> <span class="nx">result</span> <span class="o">=</span> <span class="nx">functionCallable</span><span class="p">.</span><span class="nx">parseResult</span><span class="p">(</span><span class="nx">callResultData</span><span class="p">);</span>
</pre></div>
</div>
</div>
<div class="literal-block-wrapper docutils container" id="id22">
<div class="code-block-caption"><span class="caption-text"><em>Function Description — ethers v4</em></span><a class="headerlink" href="#id22" title="Permalink to this code"></a></div>
<div class="highlight-javascript notranslate"><div class="highlight"><pre><span></span><span class="kd">let</span> <span class="nx">address</span> <span class="o">=</span> <span class="s2">&quot;0x8B40a2E27C5E87aa66DfA7F80BF675176F49DCA7&quot;</span><span class="p">;</span>
<span class="kd">let</span> <span class="nx">value</span> <span class="o">=</span> <span class="mi">1000</span><span class="p">;</span>
<span class="c1">// Solidity: function someFunc(address foo, uint256 bar) constant returns (address result)</span>
<span class="kd">let</span> <span class="nx">functionInfo</span> <span class="o">=</span> <span class="nx">iface</span><span class="p">.</span><span class="nx">functions</span><span class="p">.</span><span class="nx">someFunc</span><span class="p">;</span>
<span class="c1">// functionInfo</span>
<span class="c1">// - type: &quot;call&quot; (or &quot;transaction&quot; for non-constant functions)</span>
<span class="c1">// - name: &quot;someFunc&quot;</span>
<span class="c1">// - signature: &quot;someFunc(address,uint256)&quot;</span>
<span class="c1">// - sighash: &quot;0xd90a6a67&quot;</span>
<span class="c1">// - inputs: [ { name: foo&quot;, type: &quot;bar&quot; }, { name: &quot;bar&quot;, type: &quot;uint256&quot; } ]</span>
<span class="c1">// - outputs: [ { name: &quot;result&quot;, type: &quot;address&quot; } ]</span>
<span class="c1">// - payable: false</span>
<span class="c1">// - encode: (params) =&gt; string</span>
<span class="c1">// - decode: (data) =&gt; any</span>
<span class="c1">// Note: This takes in an array; it no longer uses ...args</span>
<span class="kd">let</span> <span class="nx">data</span> <span class="o">=</span> <span class="nx">functionInfo</span><span class="p">.</span><span class="nx">encode</span><span class="p">([</span> <span class="nx">address</span><span class="p">,</span> <span class="nx">value</span> <span class="p">]);</span>
<span class="kd">let</span> <span class="nx">result</span> <span class="o">=</span> <span class="nx">functionInfo</span><span class="p">.</span><span class="nx">decode</span><span class="p">(</span><span class="nx">callResultData</span><span class="p">);</span>
</pre></div>
</div>
</div>
<div class="literal-block-wrapper docutils container" id="id23">
<div class="code-block-caption"><span class="caption-text"><em>Event Description — ethers v3</em></span><a class="headerlink" href="#id23" title="Permalink to this code"></a></div>
<div class="highlight-javascript notranslate"><div class="highlight"><pre><span></span><span class="c1">// Solidity: event SomeEvent(address foo, uint256 bar)</span>
<span class="kd">let</span> <span class="nx">eventInfo</span> <span class="o">=</span> <span class="nx">iface</span><span class="p">.</span><span class="nx">events</span><span class="p">.</span><span class="nx">SomeEvent</span><span class="p">;</span>
<span class="c1">// eventInfo</span>
<span class="c1">// - topics: [ ethers.utils.id(&quot;SomeEvent(address,uint256)&quot;) ]</span>
<span class="c1">// - anonymous: false</span>
<span class="c1">// - name: &quot;SomeEvent&quot;</span>
<span class="c1">// - signature: &quot;SomeEvent(address,uint256)&quot;</span>
<span class="c1">// - type: &quot;event&quot;</span>
<span class="c1">// - inputs: { names: [ &#39;foo&#39;, &#39;bar&#39; ], types: [ &#39;address&#39;, &#39;uint256&#39; ] }</span>
<span class="c1">// - parse: (topics, data) =&gt; Result</span>
</pre></div>
</div>
</div>
<div class="literal-block-wrapper docutils container" id="id24">
<div class="code-block-caption"><span class="caption-text"><em>Event Description — ethers v4</em></span><a class="headerlink" href="#id24" title="Permalink to this code"></a></div>
<div class="highlight-javascript notranslate"><div class="highlight"><pre><span></span><span class="c1">// Solidity: event SomeEvent(address foo, uint256 bar)</span>
<span class="kd">let</span> <span class="nx">eventInfo</span> <span class="o">=</span> <span class="nx">iface</span><span class="p">.</span><span class="nx">events</span><span class="p">.</span><span class="nx">SomeEvent</span><span class="p">;</span>
<span class="c1">// eventInfo</span>
<span class="c1">// - name: &quot;SomeEvent&quot;</span>
<span class="c1">// - signature: &quot;SomeEvent(address,bar)&quot;</span>
<span class="c1">// - inputs: [ { name: &quot;foo&quot;, type: &quot;address&quot; }, { name: &quot;bar&quot;, type: &quot;uint256&quot; } ]</span>
<span class="c1">// - anonymous: false</span>
<span class="c1">// - topic: ethers.utils.id(&quot;SomeEvent(address,uint256)&quot;)</span>
<span class="c1">// - encodeTopics: (Array&lt;any&gt;) =&gt; Array&lt;string&gt;</span>
<span class="c1">// - decode: (data, topics) =&gt; Result</span>
<span class="c1">// Create event filter topics</span>
<span class="kd">let</span> <span class="nx">address</span> <span class="o">=</span> <span class="s1">&#39;0x8B40a2E27C5E87aa66DfA7F80BF675176F49DCA7&#39;</span><span class="p">;</span>
<span class="nx">eventInfo</span><span class="p">.</span><span class="nx">encodeTopics</span><span class="p">(</span><span class="nx">address</span><span class="p">,</span> <span class="kc">null</span><span class="p">)</span>
<span class="c1">// topics: [</span>
<span class="c1">// &quot;0xdde371250dcd21c331edbb965b9163f4898566e8c60e28868533281edf66ab03&quot;,</span>
<span class="c1">// &quot;0x0000000000000000000000008b40a2e27c5e87aa66dfa7f80bf675176f49dca7&quot;</span>
<span class="c1">// ]</span>
</pre></div>
</div>
</div>
</div>
<hr class="docutils" />
<div class="section" id="networks">
<h3>Networks<a class="headerlink" href="#networks" title="Permalink to this headline"></a></h3>
<div class="literal-block-wrapper docutils container" id="id25">
<div class="code-block-caption"><span class="caption-text"><em>Getting Network Info - ethers v3</em></span><a class="headerlink" href="#id25" title="Permalink to this code"></a></div>
<div class="highlight-javascript notranslate"><div class="highlight"><pre><span></span><span class="kd">let</span> <span class="nx">network</span> <span class="o">=</span> <span class="nx">ethers</span><span class="p">.</span><span class="nx">providers</span><span class="p">.</span><span class="nx">getNetwork</span><span class="p">(</span><span class="s1">&#39;ropsten&#39;</span><span class="p">)</span>
</pre></div>
</div>
</div>
<div class="literal-block-wrapper docutils container" id="id26">
<div class="code-block-caption"><span class="caption-text"><em>Getting Network Info - ethers v4</em></span><a class="headerlink" href="#id26" title="Permalink to this code"></a></div>
<div class="highlight-javascript notranslate"><div class="highlight"><pre><span></span><span class="kd">let</span> <span class="nx">network</span> <span class="o">=</span> <span class="nx">ethers</span><span class="p">.</span><span class="nx">utils</span><span class="p">.</span><span class="nx">getNetwork</span><span class="p">(</span><span class="s1">&#39;ropsten&#39;</span><span class="p">);</span>
<span class="c1">// Networks may now also be found by their network ID</span>
<span class="kd">let</span> <span class="nx">network</span> <span class="o">=</span> <span class="nx">ethers</span><span class="p">.</span><span class="nx">utils</span><span class="p">.</span><span class="nx">getNetwork</span><span class="p">(</span><span class="mi">3</span><span class="p">);</span>
<span class="c1">// And networks can be validated as an object</span>
<span class="kd">let</span> <span class="nx">network</span> <span class="o">=</span> <span class="nx">ethers</span><span class="p">.</span><span class="nx">utils</span><span class="p">.</span><span class="nx">getNetwork</span><span class="p">({</span> <span class="nx">name</span><span class="o">:</span> <span class="s2">&quot;custom&quot;</span><span class="p">,</span> <span class="nx">chainId</span><span class="o">:</span> <span class="mi">1337</span> <span class="p">});</span>
<span class="c1">// Validation fails; this will throw an error, since Rinkeby is not</span>
<span class="c1">// chain ID 1 (homestead is)</span>
<span class="kd">let</span> <span class="nx">network</span> <span class="o">=</span> <span class="nx">ethers</span><span class="p">.</span><span class="nx">utils</span><span class="p">.</span><span class="nx">getNetwork</span><span class="p">({</span> <span class="nx">name</span><span class="o">:</span> <span class="s2">&quot;rinkeby&quot;</span><span class="p">,</span> <span class="nx">chainId</span><span class="o">:</span> <span class="mi">1</span> <span class="p">});</span>
</pre></div>
</div>
</div>
</div>
<hr class="docutils" />
<div class="section" id="parsing-transactions">
<h3>Parsing Transactions<a class="headerlink" href="#parsing-transactions" title="Permalink to this headline"></a></h3>
<p>The transaction parsing was moved out of the Wallet and into its own class
in the utilities, along with a general serialization API.</p>
<div class="literal-block-wrapper docutils container" id="id27">
<div class="code-block-caption"><span class="caption-text"><em>ethers v3</em></span><a class="headerlink" href="#id27" title="Permalink to this code"></a></div>
<div class="highlight-javascript notranslate"><div class="highlight"><pre><span></span><span class="kd">let</span> <span class="nx">tx</span> <span class="o">=</span> <span class="nx">ethers</span><span class="p">.</span><span class="nx">Wallet</span><span class="p">.</span><span class="nx">parseTransaction</span><span class="p">(</span><span class="nx">rawTransaction</span><span class="p">);</span>
</pre></div>
</div>
</div>
<div class="literal-block-wrapper docutils container" id="id28">
<div class="code-block-caption"><span class="caption-text"><em>ethers v4</em></span><a class="headerlink" href="#id28" title="Permalink to this code"></a></div>
<div class="highlight-javascript notranslate"><div class="highlight"><pre><span></span><span class="kd">let</span> <span class="nx">tx</span> <span class="o">=</span> <span class="nx">ethers</span><span class="p">.</span><span class="nx">utils</span><span class="p">.</span><span class="nx">parseTransaction</span><span class="p">(</span><span class="nx">rawTransaction</span><span class="p">);</span>
</pre></div>
</div>
</div>
</div>
<hr class="docutils" />
<div class="section" id="custom-signer">
<h3>Custom Signer<a class="headerlink" href="#custom-signer" title="Permalink to this headline"></a></h3>
<div class="literal-block-wrapper docutils container" id="id29">
<div class="code-block-caption"><span class="caption-text"><em>Custome Signer — ethers v3</em></span><a class="headerlink" href="#id29" title="Permalink to this code"></a></div>
<div class="highlight-javascript notranslate"><div class="highlight"><pre><span></span><span class="kd">let</span> <span class="nx">signer</span> <span class="o">=</span> <span class="p">{</span>
<span class="c1">// Required</span>
<span class="nx">getAddress</span><span class="o">:</span> <span class="kd">function</span><span class="p">()</span> <span class="p">{</span> <span class="p">...</span> <span class="p">},</span>
<span class="nx">provider</span><span class="o">:</span> <span class="nx">provider</span><span class="p">,</span>
<span class="c1">// Optional</span>
<span class="nx">estimateGas</span><span class="o">:</span> <span class="kd">function</span><span class="p">(</span><span class="nx">tx</span><span class="p">)</span> <span class="p">{</span> <span class="p">...</span> <span class="p">},</span>
<span class="nx">sendTransaction</span><span class="o">:</span> <span class="kd">function</span><span class="p">(</span><span class="nx">tx</span><span class="p">)</span> <span class="p">{</span> <span class="p">...</span> <span class="p">},</span>
<span class="nx">sign</span><span class="o">:</span> <span class="kd">function</span><span class="p">(</span><span class="nx">tx</span><span class="p">)</span> <span class="p">{</span> <span class="p">...</span> <span class="p">},</span>
<span class="p">};</span>
</pre></div>
</div>
</div>
<div class="literal-block-wrapper docutils container" id="id30">
<div class="code-block-caption"><span class="caption-text"><em>Custom Signer — JavaScript — ethers v4</em></span><a class="headerlink" href="#id30" title="Permalink to this code"></a></div>
<div class="highlight-javascript notranslate"><div class="highlight"><pre><span></span><span class="kd">function</span> <span class="nx">CustomSigner</span> <span class="p">{</span>
<span class="nx">ethers</span><span class="p">.</span><span class="nx">Signer</span><span class="p">.</span><span class="nx">call</span><span class="p">(</span><span class="k">this</span><span class="p">);</span>
<span class="c1">// Optional</span>
<span class="k">this</span><span class="p">.</span><span class="nx">provider</span> <span class="o">=</span> <span class="nx">provider</span><span class="p">;</span>
<span class="p">}</span>
<span class="nx">inherits</span><span class="p">(</span><span class="nx">CustomSigner</span><span class="p">,</span> <span class="nx">ethers</span><span class="p">.</span><span class="nx">Signer</span><span class="p">);</span>
<span class="c1">// Required</span>
<span class="nx">CustomSigner</span><span class="p">.</span><span class="nx">prototype</span><span class="p">.</span><span class="nx">getAddress</span> <span class="o">=</span> <span class="p">()</span> <span class="p">=&gt;</span> <span class="p">{</span> <span class="p">...</span> <span class="p">};</span>
<span class="nx">CustomSigner</span><span class="p">.</span><span class="nx">prototype</span><span class="p">.</span><span class="nx">sendTransaction</span> <span class="o">=</span> <span class="p">(</span><span class="nx">tx</span><span class="p">)</span> <span class="p">=&gt;</span> <span class="p">{</span> <span class="p">...</span> <span class="p">};</span>
<span class="nx">CustomSigner</span><span class="p">.</span><span class="nx">prototype</span><span class="p">.</span><span class="nx">signMessage</span> <span class="o">=</span> <span class="p">(</span><span class="nx">message</span><span class="p">)</span> <span class="p">=&gt;</span> <span class="p">{</span> <span class="p">...</span> <span class="p">};</span>
<span class="c1">// Optional</span>
<span class="nx">CustomSigner</span><span class="p">.</span><span class="nx">prototype</span><span class="p">.</span><span class="nx">connect</span> <span class="o">=</span> <span class="p">(</span><span class="nx">provider</span><span class="p">)</span> <span class="p">=&gt;</span> <span class="p">{</span> <span class="p">...</span> <span class="p">};</span>
</pre></div>
</div>
</div>
<div class="literal-block-wrapper docutils container" id="id31">
<div class="code-block-caption"><span class="caption-text"><em>Custom Signer — TypeScript — ethers v4</em></span><a class="headerlink" href="#id31" title="Permalink to this code"></a></div>
<div class="highlight-javascript notranslate"><div class="highlight"><pre><span></span><span class="kr">import</span> <span class="p">{</span>
<span class="nx">Signer</span><span class="p">,</span>
<span class="nx">utils</span>
<span class="p">}</span> <span class="nx">from</span> <span class="s1">&#39;ethers&#39;</span><span class="p">;</span>
<span class="kr">import</span> <span class="p">{</span>
<span class="nx">Provider</span><span class="p">,</span>
<span class="nx">TransactionRequest</span><span class="p">,</span>
<span class="nx">TransactionReqponse</span>
<span class="p">}</span> <span class="nx">from</span> <span class="s1">&#39;ethers/providers&#39;</span><span class="p">;</span>
<span class="kr">class</span> <span class="nx">CustomSigner</span> <span class="kr">extends</span> <span class="nx">Signer</span> <span class="p">{</span>
<span class="k">this</span><span class="p">.</span><span class="nx">provider</span> <span class="o">=</span> <span class="nx">provider</span><span class="p">;</span>
<span class="nx">readony</span> <span class="nx">provider</span><span class="o">:</span> <span class="nx">Provider</span><span class="p">;</span>
<span class="nx">constructor</span><span class="p">(</span><span class="nx">provider</span><span class="p">)</span> <span class="p">{</span>
<span class="kr">super</span><span class="p">();</span>
<span class="c1">// Optional</span>
<span class="k">this</span><span class="p">.</span><span class="nx">provider</span> <span class="o">=</span> <span class="c1">// ...</span>
<span class="p">}</span>
<span class="nx">getAddress</span><span class="p">()</span> <span class="p">{</span>
<span class="c1">// Return a promise to the address</span>
<span class="p">};</span>
<span class="nx">sendTransaction</span> <span class="o">=</span> <span class="p">(</span><span class="nx">transaction</span><span class="o">:</span> <span class="nx">TransactionRequest</span><span class="p">)</span><span class="o">:</span> <span class="nb">Promise</span><span class="o">&lt;</span><span class="nx">TransaxctinResponse</span><span class="o">&gt;</span> <span class="p">{</span>
<span class="c1">// This will popualte missing properties, like nonce, gasLimit, etc</span>
<span class="k">return</span> <span class="nx">utils</span><span class="p">.</span><span class="nx">populateTransaction</span><span class="p">(</span><span class="nx">transaction</span><span class="p">).</span><span class="nx">then</span><span class="p">((</span><span class="nx">tx</span><span class="p">)</span> <span class="p">=&gt;</span> <span class="p">{</span>
<span class="c1">// Send the transaction and resolve the transaction</span>
<span class="p">});</span>
<span class="p">};</span>
<span class="nx">signMessage</span><span class="p">(</span><span class="nx">message</span><span class="o">:</span> <span class="nx">string</span> <span class="o">|</span> <span class="nx">ethers</span><span class="p">.</span><span class="nx">utils</span><span class="p">.</span><span class="nx">Arrayish</span><span class="p">)</span><span class="o">:</span> <span class="nb">Promise</span><span class="o">&lt;</span><span class="nx">string</span><span class="o">&gt;</span> <span class="p">{</span>
<span class="kd">let</span> <span class="nx">dataToSign</span><span class="o">:</span> <span class="nx">Uint8Array</span> <span class="o">=</span> <span class="nx">utils</span><span class="p">.</span><span class="nx">hashMessage</span><span class="p">(</span><span class="nx">message</span><span class="p">);;</span>
<span class="c1">// Sign ths dataToSign and resolve teh flat-format signature</span>
<span class="p">};</span>
<span class="c1">// Optional; highly recommended</span>
<span class="nx">connect</span><span class="p">(</span><span class="nx">provider</span><span class="o">:</span> <span class="nx">Provider</span><span class="p">)</span><span class="o">:</span> <span class="nx">CustomSigner</span> <span class="p">{</span>
<span class="k">return</span> <span class="k">new</span> <span class="nx">CustomSigner</span><span class="p">(</span><span class="nx">provider</span><span class="p">);</span>
<span class="p">}</span>
<span class="p">}</span>
</pre></div>
</div>
</div>
</div>
<hr class="docutils" />
<div class="section" id="default-provider">
<h3>Default Provider<a class="headerlink" href="#default-provider" title="Permalink to this headline"></a></h3>
<div class="literal-block-wrapper docutils container" id="id32">
<div class="code-block-caption"><span class="caption-text"><em>Default Provider — ethers v3</em></span><a class="headerlink" href="#id32" title="Permalink to this code"></a></div>
<div class="highlight-javascript notranslate"><div class="highlight"><pre><span></span><span class="kd">let</span> <span class="nx">provider</span> <span class="o">=</span> <span class="nx">ethers</span><span class="p">.</span><span class="nx">providers</span><span class="p">.</span><span class="nx">getDefaultProvider</span><span class="p">();</span>
</pre></div>
</div>
</div>
<div class="literal-block-wrapper docutils container" id="id33">
<div class="code-block-caption"><span class="caption-text"><em>Default Provider — ethers v4</em></span><a class="headerlink" href="#id33" title="Permalink to this code"></a></div>
<div class="highlight-javascript notranslate"><div class="highlight"><pre><span></span><span class="kd">let</span> <span class="nx">provider</span> <span class="o">=</span> <span class="nx">ethers</span><span class="p">.</span><span class="nx">getDefaultProvider</span><span class="p">();</span>
</pre></div>
</div>
</div>
</div>
<hr class="docutils" />
<div class="section" id="big-number">
<h3>Big Number<a class="headerlink" href="#big-number" title="Permalink to this headline"></a></h3>
<div class="literal-block-wrapper docutils container" id="id34">
<div class="code-block-caption"><span class="caption-text"><em>isBigNumber — ethers v3</em></span><a class="headerlink" href="#id34" title="Permalink to this code"></a></div>
<div class="highlight-javascript notranslate"><div class="highlight"><pre><span></span><span class="kd">let</span> <span class="nx">checkBigNumber</span> <span class="o">=</span> <span class="nx">ethers</span><span class="p">.</span><span class="nx">utils</span><span class="p">.</span><span class="nx">isBigNumber</span><span class="p">(</span><span class="nx">value</span><span class="p">);</span>
</pre></div>
</div>
</div>
<div class="literal-block-wrapper docutils container" id="id35">
<div class="code-block-caption"><span class="caption-text"><em>isBigNumber — ethers v4</em></span><a class="headerlink" href="#id35" title="Permalink to this code"></a></div>
<div class="highlight-javascript notranslate"><div class="highlight"><pre><span></span><span class="kd">let</span> <span class="nx">checkBigNumber</span> <span class="o">=</span> <span class="nx">BigNumber</span><span class="p">.</span><span class="nx">isBigNumber</span><span class="p">(</span><span class="nx">value</span><span class="p">);</span>
</pre></div>
</div>
</div>
</div>
<hr class="docutils" />
<div class="section" id="jsonrpcprovider">
<h3>JsonRpcProvider<a class="headerlink" href="#jsonrpcprovider" title="Permalink to this headline"></a></h3>
<div class="literal-block-wrapper docutils container" id="id36">
<div class="code-block-caption"><span class="caption-text"><em>Connecting — ethers v3</em></span><a class="headerlink" href="#id36" title="Permalink to this code"></a></div>
<div class="highlight-javascript notranslate"><div class="highlight"><pre><span></span><span class="kd">let</span> <span class="nx">url</span> <span class="o">=</span> <span class="s2">&quot;http://localhost:8545&quot;</span><span class="p">;</span>
<span class="kd">let</span> <span class="nx">network</span> <span class="o">=</span> <span class="s2">&quot;rinkeby&quot;</span><span class="p">;</span>
<span class="kd">let</span> <span class="nx">provider</span> <span class="o">=</span> <span class="k">new</span> <span class="nx">ethers</span><span class="p">.</span><span class="nx">providers</span><span class="p">.</span><span class="nx">JsonRpcProvider</span><span class="p">(</span><span class="nx">url</span><span class="p">,</span> <span class="nx">network</span><span class="p">);</span>
<span class="c1">// Even if the network was wrong, this would mostly seem to work and</span>
<span class="c1">// fail once the chain ID was attempted</span>
<span class="c1">// The network was a synchronous property on Provider</span>
<span class="kd">let</span> <span class="nx">network</span> <span class="o">=</span> <span class="nx">provider</span><span class="p">.</span><span class="nx">network</span><span class="p">;</span>
</pre></div>
</div>
</div>
<div class="literal-block-wrapper docutils container" id="id37">
<div class="code-block-caption"><span class="caption-text"><em>Connecting — ethers v4</em></span><a class="headerlink" href="#id37" title="Permalink to this code"></a></div>
<div class="highlight-javascript notranslate"><div class="highlight"><pre><span></span><span class="c1">// In v4, the network is automatically determined; you may override</span>
<span class="c1">// the network, but it must match, or it will fail early</span>
<span class="kd">let</span> <span class="nx">url</span> <span class="o">=</span> <span class="s2">&quot;http://localhost:8545&quot;</span><span class="p">;</span>
<span class="kd">let</span> <span class="nx">provider</span> <span class="o">=</span> <span class="k">new</span> <span class="nx">ethers</span><span class="p">.</span><span class="nx">providers</span><span class="p">.</span><span class="nx">JsonRpcProvider</span><span class="p">(</span><span class="nx">url</span><span class="p">);</span>
<span class="c1">// The network is now an asynchronous property:</span>
<span class="nx">provider</span><span class="p">.</span><span class="nx">getNetwork</span><span class="p">().</span><span class="nx">then</span><span class="p">((</span><span class="nx">network</span><span class="p">)</span> <span class="p">=&gt;</span> <span class="p">{</span>
<span class="c1">// ...</span>
<span class="p">});</span>
<span class="c1">// One useful and common exception it that, if any async call from</span>
<span class="c1">// the provider has ever succeeded, the synchronous network property</span>
<span class="c1">// is then valid. The network property is populated before any</span>
<span class="c1">// async call is made, so once an async call has finished, the network</span>
<span class="c1">// property is available synchronously.</span>
<span class="nx">async</span> <span class="kd">function</span><span class="p">()</span> <span class="p">{</span>
<span class="nx">await</span> <span class="nx">provider</span><span class="p">.</span><span class="nx">getBlockNumber</span><span class="p">();</span>
<span class="kd">let</span> <span class="nx">network</span> <span class="o">=</span> <span class="nx">provider</span><span class="p">.</span><span class="nx">network</span><span class="p">;</span>
<span class="p">}</span>
</pre></div>
</div>
</div>
<div class="literal-block-wrapper docutils container" id="id38">
<div class="code-block-caption"><span class="caption-text"><em>Sending Transactions — ethers v3</em></span><a class="headerlink" href="#id38" title="Permalink to this code"></a></div>
<div class="highlight-javascript notranslate"><div class="highlight"><pre><span></span><span class="nx">provider</span><span class="p">.</span><span class="nx">sendTransaction</span><span class="p">(</span><span class="nx">rawTransaction</span><span class="p">).</span><span class="nx">then</span><span class="p">((</span><span class="nx">hash</span><span class="p">)</span> <span class="p">=&gt;</span> <span class="p">{</span>
<span class="c1">// Just a transaction hash</span>
<span class="p">});</span>
</pre></div>
</div>
</div>
<div class="literal-block-wrapper docutils container" id="id39">
<div class="code-block-caption"><span class="caption-text"><em>Sending Transactions — ethers v4</em></span><a class="headerlink" href="#id39" title="Permalink to this code"></a></div>
<div class="highlight-javascript notranslate"><div class="highlight"><pre><span></span><span class="nx">provider</span><span class="p">.</span><span class="nx">sendTransaction</span><span class="p">(</span><span class="nx">rawTransaction</span><span class="p">).</span><span class="nx">then</span><span class="p">((</span><span class="nx">transaction</span><span class="p">)</span> <span class="p">=&gt;</span> <span class="p">{</span>
<span class="c1">// A full Transaction Response is returned</span>
<span class="c1">// - from</span>
<span class="c1">// - to</span>
<span class="c1">// - gasLimit, gasPrice</span>
<span class="c1">// - nonce</span>
<span class="c1">// - r, s, v</span>
<span class="c1">// - wait() =&gt; Promise that resolves the Transaction Receipt once mined</span>
<span class="c1">// and rejects with an error is the stats is 0; the error</span>
<span class="c1">// will have a transactionHash property as well as a</span>
<span class="c1">// transaction property.</span>
<span class="kd">let</span> <span class="nx">hash</span> <span class="o">=</span> <span class="nx">transaction</span><span class="p">.</span><span class="nx">hash</span><span class="p">;</span>
<span class="p">});</span>
</pre></div>
</div>
</div>
</div>
<hr class="docutils" />
<div class="section" id="verifying-messages">
<h3>Verifying Messages<a class="headerlink" href="#verifying-messages" title="Permalink to this headline"></a></h3>
<p>The message verification was moved from a static class on the Wallet to the
utilities, along with a few other functions of the elliptic curve cryptographic
exposed.</p>
<div class="literal-block-wrapper docutils container" id="id40">
<div class="code-block-caption"><span class="caption-text"><em>ethers v3</em></span><a class="headerlink" href="#id40" title="Permalink to this code"></a></div>
<div class="highlight-javascript notranslate"><div class="highlight"><pre><span></span><span class="kd">let</span> <span class="nx">signingAddress</span> <span class="o">=</span> <span class="nx">ethers</span><span class="p">.</span><span class="nx">Wallet</span><span class="p">.</span><span class="nx">verifyMessage</span><span class="p">(</span><span class="nx">message</span><span class="p">,</span> <span class="nx">signature</span><span class="p">);</span>
</pre></div>
</div>
</div>
<div class="literal-block-wrapper docutils container" id="id41">
<div class="code-block-caption"><span class="caption-text"><em>ethers v4</em></span><a class="headerlink" href="#id41" title="Permalink to this code"></a></div>
<div class="highlight-javascript notranslate"><div class="highlight"><pre><span></span><span class="kd">let</span> <span class="nx">signingAddress</span> <span class="o">=</span> <span class="nx">ethers</span><span class="p">.</span><span class="nx">utils</span><span class="p">.</span><span class="nx">verifyMessage</span><span class="p">(</span><span class="nx">message</span><span class="p">,</span> <span class="nx">signature</span><span class="p">);</span>
</pre></div>
</div>
</div>
</div>
<hr class="docutils" />
<div class="section" id="waiting-for-transactions">
<h3>Waiting for Transactions<a class="headerlink" href="#waiting-for-transactions" title="Permalink to this headline"></a></h3>
<p>In v3, the <code class="docutils literal notranslate"><span class="pre">transaction.wait()</span></code> returned a Promise which would resolve to the
<strong>TransactionResponse</strong> once it is mined.</p>
<p>In v4, the <code class="docutils literal notranslate"><span class="pre">transaction.wait()</span></code> returned a Promise which would resolve to the
<strong>TransactionReceipt</strong> once it is mined.</p>
<hr class="docutils" />
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