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React, removeEventListener and bind(this) gotcha
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/* Sometimes it's pretty easy to run ito troubles with React ES6 components. | |
Consider the following code: */ | |
class EventStub extends Component { | |
componentDidMount() { | |
window.addEventListener('resize', this.onResize.bind(this)); //notice .bind | |
} | |
componentWillUnmount() { | |
window.removeEventListener('resize', this.onResize.bind(this)); | |
} | |
onResize() { | |
this.setState({width: this.div.offsetWidth}); | |
} | |
render() { return null; } | |
} | |
/* As a result EventListener won't be removed since A new function reference is created after .bind() is called. | |
(more http://stackoverflow.com/questions/11565471/removing-event-listener-which-was-added-with-bind | |
and http://alexfedoseev.com/post/65/react-event-handlers-and-context-binding). | |
Obviously this is not React's fault, it's how DOM works, but it's super easy to make a mistake. ESLint rule anyone? | |
What about solutions? Pretty straightforward one is to create bound funciton only once in constructor, | |
assign to internal prop and then use it:*/ | |
this.bound_onResize = this.onResize(bind); | |
//or replace the funtion with the bound one that allows to use same funtion: | |
this.onResize = this.onResize.bind(this); | |
//another options is to use arrow funciton on a class level so it'll capture "this" automatically, | |
//but this is as of Jan 2016 Stage 2 ES2016 (ES7) proposal and requires "babel experimental" flag | |
export class MyComponent extends Component { | |
onResize = () => this.onResize() | |
} |
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