我该如何制作一个按钮来计算在React中点击时输入到文本框中的字符数？

import React, { Component } from 'react';

class ButtonCalculator extends Component {
  constructor(props) {
    super(props);
    this.state = {
      inputValue: ''
    };
  }

  calculate = () => {
    const inputValue = this.state.inputValue;
    const charCount = inputValue.length;
    this.setState({ inputValue: charCount });
  }

  render() {
    return (
      <div>
        <input
          type="text"
          value={this.state.inputValue}
          onChange={e => this.setState({ inputValue: e.target.value })}
        />
        <button onClick={this.calculate}>计算字符数</button>
        <div>字符数：{this.state.inputValue}</div>
      </div>
    );
  }
}

export default ButtonCalculator;