React——使用生命周期写一个当前时间

import React from "react";
import ReactDOM from "react-dom";
import "./index.css";
export default class App extends React.Component {
  state = {
    timer: new Date().toLocaleTimeString(),
  };
  componentDidMount() {
    this.tick();
  }
  componentWillUnmount() {
    clearInterval(this.inderver);
  }
  tick() {
    this.inderver = setInterval(() => {
      this.setState({
        timer: new Date().toLocaleTimeString(),
      });
    }, 1000);
  }
  render() {
    return (
      <div>
        <h1>{this.state.timer}</h1>
      </div>
    );
  }
}
ReactDOM.render(<App />, document.querySelector("#root"));