Javascript删除功能 [英] Javascript delete a function

问题描述

如何删除功能

即

test=true;
delete test;
=> true

function test() {..}

delete test()
=> false

删除通常适用于变量，但不适用于函数.

Delete usually works for variables but it doesn't work for functions.

推荐答案

不，您不能删除 语言规范的一部分.

如果您在JavaScript中签出了删除运算符的说明:

If you check out the description of the delete operator in JavaScript:

如果描述[[Configurable]]为真，则

If desc.[[Configurable]] is true, then

• 从O删除名称为P的自有财产.

• Remove the own property with name P from O.

返回true.

如果转到浏览器并在控制台中运行以下命令:

If you go to the browser and run the following in the console:

>function f(){}
>Object.getOwnPropertyDescriptor(window,"f")

您会得到:

对象{值:函数，可写:true，可枚举:true，可配置:false}

但是，您可以将结果分配给不是函数的另一个值，假设这是您对该函数的最后一个引用，则会发生垃圾回收并将其取消分配.

You can however, assign the result to another value that is not a function, assuming that is your last reference to that function, garbage collection will occur and it will get de-allocated.

出于除 getOwnPropertyNames hasOwnProperty 之类的所有目的，诸如 f = undefined 之类的东西应该可以工作.在这种情况下，您可以改用functionExpression并将其分配给变量.但是，出于诸如 hasOwnProperty 之类的目的，它将失败，请在控制台中尝试！

For all purposes other than getOwnPropertyNames hasOwnProperty and such, something like f = undefined should work. For those cases, you can use a functionExpression instead and assign that to a variable instead. However, for those purposes like hasOwnProperty it will fail, try it in the console!

function f(){}
f = undefined;
window.hasOwnProperty("f");//true

关于删除的更多说明

• 当您的现代浏览器看到 delete 语句时，

  Some more notes on delete

  • When your modern browser sees a delete statement, that forces it to fall to hash map mode on objects, so delete can be very slow (perf).

    在带有垃圾收集器的托管语言中，使用 delete 可能会出现问题.您不必处理内存，语言会为您完成.

    In a managed language with a garbage collector, using delete might prove problematic. You don't have to handle your memory, the language does that for you.

    在您确实要使用诸如地图之类的对象的情况下，这是一个有效的用例，并且

    In the case you do want to use objects like a map, that's a valid use case and it's on the way :)

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