代码示例:(标识:eg_js_strict_delete)
<!DOCTYPE html>
<html>
<body>

<h1>使用 "use strict":</h1>

<h3>不允许删除变量(或对象)。</h3>

<p>在浏览器中激活调试(F12)以查看错误报告。</p>

<script>
"use strict";
var x = 3.14;
delete x;     // 会引发错误
</script>

</body>
</html>
运行结果: