When using ES6 version of defining a React Component,

DONT

class A extends React.Component {
 myFunction() {
 // you'd want to use `this` here
 }
 componentDidMount /* or some react component lifecycle method */() {
 // Never do .bind(this) at the place of subscription
 SomeEvent.subscribe(this.myFunction.bind(this));
 }
 componentWillUnmount() {
 // because, now this will not work
 SomeEvent.unsubscribe(this.myFunction.bind(this));
 }
}

DO

class B extends React.Component {
 constructor(...args) {
 super(...args);
 // bind it and make it an instance method instead of prototype method
 this.myFunction = this.myFunction.bind(this);
 }
 myFunction() { /* this */ }
 componentDidMount() {
 SomeEvent.subscribe(this.myFunction);
 }
 componentWillUnmount() {
 SomeEvent.unsubscribe(this.myFunction);
 }
}

BUT

const C = React.createClass({
 //- - - - - - ^ - the magic happens here
 myFunction() {
 // this
 },
 componentDidMount() {
 SomeEvent.subscribe(this.myFunction);
 },
 componentWillUnmount() {
 SomeEvent.unsubscribe(this.myFunction);
 }
});

Inspired from this article - [https://www.webreflection.co.uk/blog/2015/10/22/how-to-add-dom-events-listeners] by
@WebReflection

This is also, mentioned in the official React docs - [https://facebook.github.io/react/blog/2015/01/27/react-v0.13.0-beta-1.html#autobinding].