通过React js

Question

我想从列表中获取一个随机项目。 到目前为止，我设法将我的列表放在一个数组中，我试图通过一个函数得到我需要的项目，但我需要它，它是未定义的！ 我不知道我错在哪里!!!

我想在此控制台日志中看到结果

 handleChange(event) {
    this.setState({value: event.target.value});
    var NewDictionary = this.Dictionary;
    console.log(Rand(NewDictionary));
  }

整个代码在这里：

class Application extends React.Component{
  constructor(props) {
   super(props);
   this.state = {
     value:'option2',
     button:'submit',
   };
   this.Dictionary = {
     Salam:"Hi",
     khodafez:"Bye",
     are: "Yes",
     na: "No",
     shab: "Night",
     rooz: "Day",
   }
   this.handleChange = this.handleChange.bind(this);
   this.handleSubmit = this.handleSubmit.bind(this);
 }
 handleChange(event) {
    this.setState({value: event.target.value});
    var NewDictionary = this.Dictionary;
    console.log(Rand(NewDictionary));
  }
  handleSubmit(event) {
    this.setState({button: this.state.value});
    event.preventDefault();
  }

  render(){
    return(

  <form onSubmit={this.handleSubmit}>
  <div> {this.Dictionary.Salam}  </div>
  <div className="radio">
    <label>
      <input type="radio" value={this.Dictionary.Salam}
        checked={this.state.value === this.Dictionary.Salam}
        onChange={this.handleChange} />
        {this.Dictionary.Salam}
    </label>
  </div>
  <div className="radio">
    <label>
      <input type="radio" value="option2"
        checked={this.state.value === 'option2'}
        onChange={this.handleChange} />
      Option 2
    </label>
  </div>
  <div className="radio">
    <label>
      <input type="radio" value="option3"
        checked={this.state.value === 'option3'}
        onChange={this.handleChange} />
      Option 3
    </label>
  </div>
  <div className="radio">
    <label>
      <input type="radio" value="option4"
        checked={this.state.value === 'option4'}
        onChange={this.handleChange} />
        Option 4
    </label>
  </div>
  <button onClick={this.handleSubmit} className="btn btn-default" type="submit">{this.state.button}</button>
</form>

     )
   }
}
function Rand(NewDictionary){
  let i = NewDictionary.length - 1;
  const j = Math.floor(Math.random() * i);
  return NewDictionary[j];
}
ReactDOM.render(
  <Application />,
  document.getElementById('root')
);

Answer 1

这是因为NewDictionary是一个对象而不是一个数组，因此尝试通过索引获取项目将不起作用。相反，使用Object.keys(NewDictionary)创建一个键数组，然后使用随机索引获取随机键。

function Rand(NewDictionary){
  const keys = Object.keys(NewDictionary);
  let i = keys.length - 1;
  const j = Math.floor(Math.random() * i);
  return NewDictionary[keys[j]];
}