Cast a bool in JavaScript

Possible Duplicate:
How can I convert a string to boolean in JavaScript?

Hi,

How can I cast a String in Bool ?

Example: "False" to bool false

I need this for my JavaScript.

Thank you for help !

---

function castStrToBool(str){
    if (str.toLowerCase()=='false'){
       return false;
    } else if (str.toLowerCase()=='true'){
       return true;
    } else {
       return undefined;
    }
}

......但我认为乔恩的回答更好！

---

You can do this:

var bool = !!someString;

If you do that, you'll discover that the string constant "False" is in fact boolean true . Why? Because those are the rules in Javascript. Anything that's not undefined , null , the empty string ( "" ), or numeric zero is considered true .

If you want to impose your own rules for strings (a dubious idea, but it's your software), you could write a function with a lookup table to return values:

function isStringTrue(s) {
  var falses = { "false": true, "False": true };
  return !falses[s];
}

maybe.

edit — fixed the typo - thanks @Patrick

---

你可以使用类似这样的东西来为字符串提供你自己的定制“真实”测试，同时让其他类型的比较不受影响：

function isTrue(input) {
    if (typeof input == 'string') {
        return input.toLowerCase() == 'true';
    }

    return !!input;
}

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