this problem happen after react15.0 ,which event handler didn't auto bind to the component. so you must bind this to component manually whenever the event handler will be called.
there are several methods to solve the problem. but you need to know which method is best and why? In general, we recommend that binding your functions in the class constructor or use a arrow function.
// method 1： use a arrow function
class ComponentA extends React.Component {
eventHandler = () => {
console.log(this)
}
render() {
return (
);
}
// method 2: Bind your functions in the class constructor.
class ComponentA extends React.Component {
constructor(props) {
super(props);
this.eventHandler = this.eventHandler.bind(this);
}
render() {
return (
);
}
these two methods will not creates a new function when the component render everytime. so our ChildComponent will not reRender becaue of the new function props change, or may produce the performance problem.
