在React JS表单中提交之前向数据添加键和值

state = {
  formData: {}
};

handleChange = (event) => {
  const { name, value } = event.target;
  this.setState(prevState => ({
    formData: {
      ...prevState.formData,
      [name]: value
    }
  }));
}

<input type="text" name="username" onChange={this.handleChange} />
<input type="text" name="email" onChange={this.handleChange} />

handleSubmit = (event) => {
  event.preventDefault();
  const { formData } = this.state;
  // 在这里向formData添加键和值
  console.log(formData);
}

<form onSubmit={this.handleSubmit}>
  {/* 表单输入字段 */}
  <button type="submit">提交</button>
</form>

handleSubmit = (event) => {
  event.preventDefault();
  const { formData } = this.state;
  formData["key"] = "value";
  this.setState({ formData });
  console.log(formData);
}