Skip to content

Instantly share code, notes, and snippets.

@Voles
Forked from Restuta/the-bind-problem.jsx
Last active March 23, 2017 14:09
Show Gist options
  • Save Voles/a3d059c41ace356e8b3814e551ad1df5 to your computer and use it in GitHub Desktop.
Save Voles/a3d059c41ace356e8b3814e551ad1df5 to your computer and use it in GitHub Desktop.
React, removeEventListener and bind(this) gotcha
/* 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 function:
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()
}
Sign up for free to join this conversation on GitHub. Already have an account? Sign in to comment