console
class Timer extends React.Component {
constructor(props) {
super(props)
}
render() {
return (
<b>{this.props.date}</b>
)
}
}
class Clock extends React.Component {
constructor(props) {
super(props);
this.state = { date: new Date() };
}
componentDidMount() {
this.timerID = setInterval(
() => this.tick(),
1000
);
}
componentWillUnmount() {
clearInterval(this.timerID);
}
tick() {
this.setState({
date: new Date()
});
}
render() {
return (
<div>
<h1>Hello, world!</h1>
<h2>
现在是
<Timer date={this.state.date.toLocaleTimeString()}/>
</h2>
</div>
);
}
}
ReactDOM.render(
<Clock />,
document.getElementById('root')
);
<div id="root">
</div>