console的12能定时打印，就是时间不变，为什么呢

import React from "react";

class DigitalClock extends React.Component {

constructor(props) {

super(props);

this.state = {

date: new Date()

};

}

componentDidMount() {

let _this = this;

this.timer = setInterval(() => {

console.log(12);

this.setState = {

date: new Date()

};

}, 1000);

}

componentWillUnmount() {

clearInterval(this.timer);

}

render() {

return (

<div className="digital-clock-compoment">

<h1>digital clock</h1>

<h1>{this.state.date.toLocaleTimeString()}</h1>

</div>

);

}

}

export default DigitalClock;