class HelpBox extends React.Component {

constructor(props) {
    super(props);
    this.state = {
    };
    window.addEventListener("keyup", this.keyDown.bind(this), false);
}

componentDidMount() {
    this.refs.searchWord.focus();
}

componentDidUpdate(nextProps, nextState) {
    console.log('will blur', this.refs.searchWord);
    this.refs.searchWord.blur();
}

keyDown(e) {
    this.setState({});
}

render() {
    return <p>
        <input key="search" ref="searchWord" className="search" type="text"
        />
    </p>
}

}
用这个componentDidUpdate，监听keyup,输入完成失去焦点