简单教程
提交运行
代码编辑器：
<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>
运行结果：