JavaScript for/in 语句循环遍历对象的属性

<p>点击下面的按钮，循环遍历对象 "person" 的属性。</p>

<button onclick="myFunction()">点击这里</button>

<p id="demo"></p>

<script>

  function myFunction() {

    var x;

    var txt = "";

    var person = {

      fname: "Bill",

      lname: "Gates",

      age: 56

    };

    for (x in person) {

      txt = txt + person[x];

    }

    document.getElementById("demo").innerHTML = txt;

  }

</script>