状态在componentDidUpdate中不可访问

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我目前正在学习React Hooks。

我试图将状态值访问到我的类组件的componentDidUpdate（）函数中，但是没有显示出来，我也无法弄清楚为什么。相反，可以在componentDidMount（）函数中访问相同的状态值。

Can somebody please help me to understand what might be the problem and its possible solution because the same example is working fine on the youtube tutorial (link) I am referring to.

Link to CodeSandBox: link

样例代码

import React, { Component } from "react";

class ClassCounter extends Component {
  constructor(props) {
    super(props);

    this.state = {
      count: 0
    };
  }

  componentDidMount() {
    document.title = "Clicked {this.state.count} times.";
  }

  componentDidUpdate(prevProps, prevState) {
    document.title = "Clicked {this.state.count} times.";
    alert("Clicked ${this.state.count} times.");
  }

  render() {
    return (
      <div>
        <p>From Class Component.</p>
        <p>You clicked {this.state.count} number of times.</p>
        <button onClick={() => this.setState({ count: this.state.count + 1 })}>
          Clicked {this.state.count} times.
        </button>
      </div>
    );
  }
}

export default ClassCounter;