为什么JavaScript中的“假"真相? [英] Why is 'false' truthy in javascript?

问题描述

我了解到，在javascript中，空字符串是虚假的，而在JavaScript中，非空字符串是真实的.

I understand that an empty string is falsy in javascript and a not-empty string is truthy in javascript.

但是，为什么'false'在javascript中是正确的，规范中是否有明确的内容?是性能问题还是在某些情况下您希望字符串'false'代表true?

However, why is 'false' truthy in javascript, is there anything explicit in the specification? Is it a performance issue or are there situations where you would want the string 'false' to represent true?

推荐答案

回答问题的最后一部分:

Replying to the last part of your question:

在某些情况下，您希望将字符串'false'用作 代表真实吗?

Are there situations where you would want the string 'false' to represent true?

让我们考虑一下我正在测试用户输入中的空字符串.为此，我发出:

Let's consider I am testing for empty strings in my user input. To achieve that, I issue:

if (!theInput) {
    // Do something.
}

现在，如果用户在文本框中输入false，我是否希望该条件成立?当然可以.

Now do I want that condition to be true if the user enters false in the text box? Of course, I don't.

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