Question

嗨，我有这个代码与对象：

const data = [{
item1: {
    ans1: "Ich",
    ans2: "Du",
    ans3: "Jemand",
    ans4: "Egal",
    correct: 3,
    quest: "Wer hat die Kokosnuss geklaut?"
}];

和此：

    render() {
    const hereGoesMyLevelNum = this.state.level;
    const answers = data.map((answer) => {
        return (
          <ul>
              <li>{answer.item1.ans1}</li>
              <li>{answer.item1.ans2}</li>
              <li>{answer.item1.ans3}</li>
              <li>{answer.item1.ans4}</li>
          </ul>
        )
    });

    return (
      <div className="App">
         <ul>{answers}</ul>
      </div>
    );}} export default App;

我想得到＆＃34; answers.items＆＃34;通过将级别编号从状态传递给它来动态生成。类似的东西：

{answer.item{hereGoesMyLevelNum}.ans1}

你能帮帮我吗？：）

Answer 1

使用这样的方括号

{answer["item"+hereGoesMyLevelNum].ans1}

Answer 2

您可以使用Es6 Computed property keys语法（结合ES6 Template literals）。

计算属性键

const id = 1;
const myKeyName = 'key' + id;
myObject[myKeyName]

与模板文字相结合

const id = 1;
const myKeyName = `key${id}`;
myObject[myKeyName]

运行示例：

const data = [
  {
    item1: {
      ans1: "Ich",
      ans2: "Du",
      ans3: "Jemand",
      ans4: "Egal",
      correct: 3,
      quest: "Wer hat die Kokosnuss geklaut?"
    }
  }
];

class App extends React.Component {
  constructor(props) {
    super(props);
    this.state = {
      level: 1
    };
  }


  render() {
    const hereGoesMyLevelNum = this.state.level;
    return (
      <div>
        {
          data.map((answer) => {
            const lvlAnswer = `item${hereGoesMyLevelNum}`;
          return (
            <ul>
              <li>{answer[lvlAnswer].ans1}</li>
              <li>{answer[lvlAnswer].ans2}</li>
              <li>{answer[lvlAnswer].ans3}</li>
              <li>{answer[lvlAnswer].ans4}</li>
            </ul>
          )
        })
       }
      </div>
    );
  }
}

ReactDOM.render(<App />, document.getElementById("root"));

<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/react/15.1.0/react-dom.min.js"></script>
<div id="root"></div>

Answer 3

您可以使用Object.keys()从对象中动态获取属性名称。

示例

rating high low medium 1 158 1 36 2 77 2 25 3 106 10 36 4 82 56 71 5 60 97 62

如果您的对象中只有一个属性，则可以执行以下操作。

Dim myProcesses() As Process Dim myProcess As Process ' How to retrieve the program associat with pdf, when i only know the file extension ? myProcesses = Process.GetProcessesByName("AcroRd32") For Each myProcess In myProcesses If Date.Now.Ticks - myProcess.StartTime.Ticks > TimeSpan.FromSeconds(30).Ticks Then myProcess.Kill() End If Next

React：map函数中的keyname后面的变量

3 个答案: