如何在原型函数中设置对象属性(范围问题)? [英] How to set object property in prototype function (scope problem)?

问题描述

这是一件小事，我已经忘记了.可能有重复 - 我搜索了一点，找到了相似的，但找不到那么简洁.

This is something trivial, which I've forgotten. There are possibly duplicates - I searched a little, found similar, but couldn't find as concise.

   String.prototype.test = function(){this.bar = this.length + 2;}

   var str = "foo";
   str.test();

   console.log(str);                         // foo
   console.log(str.bar);                     // undefined

很确定这与 this 被困在闭包中有关.

Pretty sure it has to do with this being trapped in the closure.

推荐答案

在这种情况下与您创建字符串的方式有关.试试:

Has to do with the way you're creating your string in this case. Try:

var str = new String("Foo");

你会发现它神奇地工作.:-]

and you'll find it magically working. :-]

查看示例:http://jsbin.com/odozo3/edit

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