javascript - react 去抖得到 e.target.value undefined

Question

试图使用 lodash 的去抖动来对输入进行去抖动，但下面的代码给了我未定义的值。

const { debounce } from 'lodash'

class App extends Component {

  constructor(){
    super()
    this.handleSearch = debounce(this.handleSearch, 300)
  }

  handleSearch = e => console.log(e.target.value)

  render() {
    return <input onChange={e => this.handleSearch(e)} placeholder="Search" />
  }

}

Answer 1

这是因为 React 端的事件池。

The SyntheticEvent is pooled. This means that the SyntheticEvent object will be reused and all properties will be nullified after the event callback has been invoked. This is for performance reasons. As such, you cannot access the event in an asynchronous way.

function debounce(func, wait, immediate) {
	var timeout;
	return function() {
		var context = this, args = arguments;
		var later = function() {
			timeout = null;
			if (!immediate) func.apply(context, args);
		};
		var callNow = immediate && !timeout;
		clearTimeout(timeout);
		timeout = setTimeout(later, wait);
		if (callNow) func.apply(context, args);
	};
};

class App extends React.Component {

  constructor() {
    super()
    this.handleSearch = debounce(this.handleSearch, 2000);
  }

  handleSearch(event) {
    console.log(event.target.value);
  }

  render() {
    return <input onChange = {
      (event)=>{event.persist(); this.handleSearch(event)}
    }
    placeholder = "Search" / >
  }

}

ReactDOM.render(<App/>, document.getElementById('app'));

<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react-dom.min.js"></script>
<div id="app"></div>

https://reactjs.org/docs/events.html#event-pooling