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<body>
<h1>使用 "use strict"：</h1>
<h3>不允许删除 undeletable 属性。</h3>
<p>在浏览器中激活调试（F12）以查看错误报告。</p>
<script>
"use strict";
delete Object.prototype; // 会引发错误
</script>
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