constructor 属性返回所有 JavaScript 变量的构造函数。 - 在线编辑器

          <p> constructor 属性返回变量或对象的构造函数。</p>
<p id="demo"></p>
<script>
  document.getElementById("demo").innerHTML =
    "john".constructor + "<br>" +
    (3.14).constructor + "<br>" +
    false.constructor + "<br>" + [1, 2, 3, 4].constructor + "<br>" + {
      name: 'john',
      age: 34
    }.constructor + "<br>" +
    new Date().constructor + "<br>" +
    function() {}.constructor;
</script>
        