任何变量都可以通过设置值为 undefined 来清空。类型为 undefined.

          <p>变量可以通过设置 <b>undefined</b> 来清空。</p>
<p id="demo"></p>
<script>
  var person = {
    firstName: "John",
    lastName: "Doe",
    age: 50,
    eyeColor: "blue"
  };
  var person = undefined;
  document.getElementById("demo").innerHTML =
    person + "<br>" + typeof person;
</script>
        

任何变量都可以通过设置值为 undefined 来清空。 类型为 undefined.