mirror of
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322 lines
10 KiB
ReStructuredText
322 lines
10 KiB
ReStructuredText
.. _eth-subscribe:
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========
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web3.eth.subscribe
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========
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.. code-block:: javascript
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web3.eth.subscribe(type [, callback]);
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The ``web3.eth.subscribe`` function lets you subscribe to specifc events in the blockchain.
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----------
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Parameters
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----------
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1. ``String`` - The subscription, you want to subscribe to.
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2. ``Mixed`` - (optional) Optional additional parameters, depending on the subscription type.
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3. ``Function`` - (optional) Optional callback, returns an error object as first parameter and the result as second. Will be called for each incoming subscription.
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.. _eth-subscription-return:
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-------
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Returns
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-------
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``EventEmitter`` - A Subscription instance
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- ``subscription.id``: The subscription id, used to identify and unsubscribing the subscription.
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- ``subscription.unsubscribe([callback])``: Unsubscribes the subscription and returns `TRUE` in the callback if successfull.
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- ``on("data")`` returns ``Object``: Fires on each incoming log with the log object as argument.
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- ``on("changed")`` returns ``Object``: Fires on each log which was removed from the blockchain. The log will have the additional property ``"removed: true"``.
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- ``on("error")`` returns ``Object``: Fires when an error in the subscription occours.
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----------------
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Callback returns
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----------------
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- ``Mixed`` - depends on the subscription, see the different subscriptions for more.
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-------
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Example
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-------
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.. code-block:: javascript
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var subscription = web3.eth.subscribe('logs', {
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address: '0x123456..',
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topics: ['0x12345...']
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}, function(error, result){
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if (!error)
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console.log(log);
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});
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// unsubscribes the subscription
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subscription.unsubscribe(function(error, success){
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if(success)
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console.log('Successfully unsubscribed!');
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});
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------------------------------------------------------------------------------
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web3.eth.subscribe('pendingTransactions')
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=====================
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.. code-block:: javascript
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web3.eth.subscribe('pendingTransactions' [, callback]);
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Subscribes to incoming pending transactions.
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----------
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Parameters
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----------
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1. ``String`` - ``"pendingTransactions"``, the type of the subscription.
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2. ``Function`` - (optional) Optional callback, returns an error object as first parameter and the result as second. Will be called for each incoming subscription.
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-------
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Returns
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-------
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``EventEmitter``: An :ref:`subscription instance <eth-subscription-return>` as an event emitter with the following events:
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- ``"data"`` returns ``Object``: Fires on each incoming pending transaction.
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- ``"error"`` returns ``Object``: Fires when an error in the subscription occours.
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For the structure of the returned object see :ref:`web3.eth.getTransaction() return values <eth-gettransaction-return>`.
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----------------
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Callback returns
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----------------
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1. ``Object|Null`` - First parameter is an error object if the subscription failed.
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2. ``Object`` - The block header object like above.
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-------
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Example
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-------
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.. code-block:: javascript
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var subscription = web3.eth.subscribe('pendingTransactions', function(error, result){
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if (!error)
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console.log(transaction);
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})
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.on("data", function(transaction){
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});
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// unsubscribes the subscription
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subscription.unsubscribe(function(error, success){
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if(success)
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console.log('Successfully unsubscribed!');
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});
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------------------------------------------------------------------------------
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web3.eth.subscribe('newBlockHeaders')
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=====================
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.. code-block:: javascript
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web3.eth.subscribe('newBlockHeaders' [, callback]);
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Subscribes to incoming block headers. This can be used as timer to check for changes on the blockchain.
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----------
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Parameters
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----------
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1. ``String`` - ``"newBlockHeaders"``, the type of the subscription.
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2. ``Function`` - (optional) Optional callback, returns an error object as first parameter and the result as second. Will be called for each incoming subscription.
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-------
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Returns
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-------
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``EventEmitter``: An :ref:`subscription instance <eth-subscription-return>` as an event emitter with the following events:
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- ``"data"`` returns ``Object``: Fires on each incoming block header.
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- ``"error"`` returns ``Object``: Fires when an error in the subscription occours.
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The structure of a returned block header is as follows:
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- ``Number`` - **number**: The block number. ``null`` when its pending block.
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- ``String`` 32 Bytes - **hash**: Hash of the block. ``null`` when its pending block.
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- ``String`` 32 Bytes - **parentHash**: Hash of the parent block.
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- ``String`` 8 Bytes - **nonce**: Hash of the generated proof-of-work. ``null`` when its pending block.
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- ``String`` 32 Bytes - **sha3Uncles**: SHA3 of the uncles data in the block.
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- ``String`` 256 Bytes - **logsBloom**: The bloom filter for the logs of the block. ``null`` when its pending block.
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- ``String`` 32 Bytes - **transactionsRoot**: The root of the transaction trie of the block
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- ``String`` 32 Bytes - **stateRoot**: The root of the final state trie of the block.
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- ``String`` 32 Bytes - **receiptRoot**: The root of the receipts.
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- ``String`` - **miner**: The address of the beneficiary to whom the mining rewards were given.
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- ``String`` - **extraData**: The "extra data" field of this block.
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- ``Number`` - **gasLimit**: The maximum gas allowed in this block.
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- ``Number`` - **gasUsed**: The total used gas by all transactions in this block.
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- ``Number`` - **timestamp**: The unix timestamp for when the block was collated.
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----------------
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Callback returns
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----------------
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1. ``Object|Null`` - First parameter is an error object if the subscription failed.
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2. ``Object`` - The block header object like above.
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-------
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Example
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-------
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.. code-block:: javascript
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var subscription = web3.eth.subscribe('newBlockHeaders', function(error, result){
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if (!error)
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console.log(blockHeader);
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})
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.on("data", function(blockHeader){
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});
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// unsubscribes the subscription
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subscription.unsubscribe(function(error, success){
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if(success)
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console.log('Successfully unsubscribed!');
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});
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------------------------------------------------------------------------------
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web3.eth.subscribe('syncing')
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=====================
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.. code-block:: javascript
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web3.eth.subscribe('syncing' [, callback]);
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Subscribe to syncing events. This will return an object when the node is syncing and when its finished syncing will return ``FALSE``.
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----------
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Parameters
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----------
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1. ``String`` - ``"syncing"``, the type of the subscription.
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2. ``Function`` - (optional) Optional callback, returns an error object as first parameter and the result as second. Will be called for each incoming subscription.
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-------
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Returns
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-------
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``EventEmitter``: An :ref:`subscription instance <eth-subscription-return>` as an event emitter with the following events:
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- ``"data"`` returns ``Object``: Fires on each incoming sync object as argument.
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- ``"changed"`` returns ``Object``: Fires when the synchronisation is started with ``TRUE`` and when finsihed with ``FALSE``.
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- ``"error"`` returns ``Object``: Fires when an error in the subscription occours.
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For the structure of a returned event ``Object`` see :ref:`web3.eth.isSyncing return values <eth-issyncing-return>`.
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----------------
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Callback returns
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----------------
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1. ``Object|Null`` - First parameter is an error object if the subscription failed.
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2. ``Object|Boolean`` - The syncing object, when started it will return ``TRUE`` once or when finished it will return `FALSE` once.
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-------
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Example
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-------
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.. code-block:: javascript
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var subscription = web3.eth.subscribe('syncing', function(error, sync){
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if (!error)
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console.log(sync);
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})
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.on("data", function(sync){
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// show some syncing stats
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})
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.on("changed", function(isSyncing){
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if(isSyncing) {
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// stop app operation
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} else {
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// regain app operation
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}
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});
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// unsubscribes the subscription
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subscription.unsubscribe(function(error, success){
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if(success)
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console.log('Successfully unsubscribed!');
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});
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------------------------------------------------------------------------------
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web3.eth.subscribe('logs')
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=====================
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.. code-block:: javascript
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web3.eth.subscribe('logs', options [, callback]);
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Subscribes to incoming logs, filtered by the given options.
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----------
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Parameters
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----------
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1. ``String`` - ``"logs"``, the type of the subscription.
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2. ``Object`` - The subscription options
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- ``Number`` - **fromBlock**: The number of the earliest block. By default ``null``.
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- ``String`` - **address**: An address or a list of addresses to only get logs from particular account(s).
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- ``Array`` - **topics**: An array of values which must each appear in the log entries. The order is important, if you want to leave topics out use ``null``, e.g. ``[null, '0x00...']``. You can also pass another array for each topic with options for that topic e.g. ``[null, ['option1', 'option2']]``
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3. ``Function`` - (optional) Optional callback, returns an error object as first parameter and the result as second. Will be called for each incoming subscription.
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-------
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Returns
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-------
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``EventEmitter``: An :ref:`subscription instance <eth-subscription-return>` as an event emitter with the following events:
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- ``"data"`` returns ``Object``: Fires on each incoming log with the log object as argument.
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- ``"changed"`` returns ``Object``: Fires on each log which was removed from the blockchain. The log will have the additional property ``"removed: true"``.
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- ``"error"`` returns ``Object``: Fires when an error in the subscription occours.
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For the structure of a returned event ``Object`` see :ref:`web3.eth.getPastEvents return values <eth-getpastlogs-return>`.
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----------------
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Callback returns
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----------------
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1. ``Object|Null`` - First parameter is an error object if the subscription failed.
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2. ``Object`` - The log object like in :ref:`web3.eth.getPastEvents return values <eth-getpastlogs-return>`.
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-------
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Example
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-------
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.. code-block:: javascript
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var subscription = web3.eth.subscribe('logs', {
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address: '0x123456..',
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topics: ['0x12345...']
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}, function(error, result){
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if (!error)
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console.log(log);
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})
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.on("data", function(log){
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})
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.on("changed", function(log){
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});
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// unsubscribes the subscription
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subscription.unsubscribe(function(error, success){
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if(success)
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console.log('Successfully unsubscribed!');
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});
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