35 lines
1.6 KiB
Markdown
35 lines
1.6 KiB
Markdown
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Timers are an important part of an application and React Native implements the [browser timers](https://developer.mozilla.org/en-US/Add-ons/Code_snippets/Timers).
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## Timers
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- setTimeout, clearTimeout
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- setInterval, clearInterval
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- setImmediate, clearImmediate
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- requestAnimationFrame, cancelAnimationFrame
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`requestAnimationFrame(fn)` is the exact equivalent of `setTimeout(fn, 0)`, they are triggered right after the screen has been flushed.
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`setImmediate` is executed at the end of the current JavaScript execution block, right before sending the batched response back to native. Note that if you call `setImmediate` within a `setImmediate` callback, it will be executed right away, it won't yield back to native in between.
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The `Promise` implementation uses `setImmediate` its asynchronicity primitive.
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## TimerMixin
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We found out that the primary cause of fatals in apps created with React Native was due to timers firing after a component was unmounted. To solve this recurring issue, we introduced `TimerMixin`. If you include `TimerMixin`, then you can replace your calls to `setTimeout(fn, 500)` with `this.setTimeout(fn, 500)` (just prepend `this.`) and everything will be properly cleaned up for you when the component unmounts.
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```javascript
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var { TimerMixin } = React;
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var Component = React.createClass({
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mixins: [TimerMixin],
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componentDidMount: function() {
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this.setTimeout(
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() => { console.log('I do not leak!'); },
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500
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);
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}
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});
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```
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We highly recommend never using bare timers and always using this mixin, it will save you from a lot of hard to track down bugs.
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