为什么即使没有从对象中删除属性，删除操作符也返回true [英] Why delete operator returns true even if property wasn't deleted from an object

问题描述

>>> var par = {a: 1, b: 2};
undefined
>>> var ch = Object.create(par);
undefined
>>> delete ch.a
true
>>> ch
Object { a=1, b=2}

推荐答案

您误解了删除操作返回的内容:

You misunderstood what delete returns:

如果该属性是自己的不可配置属性，则以严格模式抛出(在非严格条件下返回false).在所有其他情况下返回true. ( https://developer.mozilla.org/zh- US/docs/Web/JavaScript/Reference/Operators/delete )

delete ch.a试图在ch中找到属性a，失败(由于ch没有这样的 own 属性)，什么也不做，很高兴地返回了true.如果您写了delete ch.foobar，结果将是相同的.但是，如果您尝试使用不可配置的属性(例如delete ch.__proto__)，则结果将为false.

delete ch.a tries to locate the property a in ch, fails (since ch doesn't have such own property), does nothing and happily returns true. If you wrote delete ch.foobar, the result would be the same. If however, you tried a non-configurable property (e.g. delete ch.__proto__), the result would be false.

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