从原型函数更新对象值 [英] Updating object value from prototype function

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问题描述

我正在尝试这样做:

String.prototype.clear = function(){
    alert(this.value);
    this = ''; // I want to set value to '' here
}

var temp = 'Hello';
temp.clear();// After this step temp should be ''

但是我收到了无效的左手分配错误。我发现这个问题作为参考,但它并不是我想要的。
我也发现'this'是不可变的。

But I'm getting invalid left hand assignment error. and I found this question as reference, but it's not really what I want. I also find out that 'this' is Immutable.

那么,有什么方法可以完成我的任务吗?我不是在任何地方使用它。只是在玩耍。
谢谢。

So, is there any way to do my task? I'm not using it any where. Just playing around. Thanks.

推荐答案

缩短期限:

你不能。

字符串是不可变的。一旦创建,就永远不能更改字符串。

Strings are immutable. Once it is made, a string can never be changed.

您必须将字符串设置为空字符串以清除它

You have to set your string to an empty string to "clear" it

var str = "String";
str='';

请注意,这不会更改字符串,但会设置 str 到一个新的String实例,旧的实例收集垃圾

Note that this won't change the string but sets str to a new Instance of a String, the old one gets garbage collected

它比调用Prototypes方法更短对象将完全相同。 你不必使用原生对象原型进行调整

It is even shorter then calling a Prototypes method of the Object which would do exactly the same. And you don't have to temper with the native Objects prototypes

编辑 - Thx for指出 Florian Margaine

Edit - Thx for pointing that out Florian Margaine

如果你有很多事情发生设置空字符串并可能改变你未来的清算定义,你可以使用一个返回``或空字符串的函数

If you have many occurences of setting empty Strings and might change your future "definition" of clearing, you could either use a funciton that returns `` or a empty String

function clearString () {
    return ''
}
var str = "Asd"
var str = clearString()

或者只是将变量设置为空字符串

Or simply Set a variable to an empty String

var emptyString = ''
var str = "Asd"
str = emptyString //''

现在,如果您想将''更改为 null undefined

Now if you want to change '' into null or undefined

var emptyString = null

哪个也可以,因为原始数据类型被传递为值而非参考

Which would work as well, since primitive data types are being passed as value and not by reference

但我建议不要修改像这样的对象原型

But i would suggest not modifying an Objects prototype for something like this

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