将true或falsy转换为一个明确的布尔值，即True或False [英] Convert truthy or falsy to an explicit boolean, i.e. to True or False

问题描述

我有一个变量.我们称之为toto.

I have a variable. Let's call it toto.

此toto可以设置为undefined，null，字符串或对象.

This toto can be set to undefined, null, a string, or an object.

我想检查是否将toto设置为数据，即是否设置为字符串或对象，而不是undefined或null，并在另一个变量中设置相应的布尔值.

I would like to check if toto is set to a data, which means set to a string or an object, and neither undefined nor null, and set corresponding boolean value in another variable.

我想到了语法!!，它看起来像这样:

I thought of the syntax !!, that would look like this:

var tata = !!toto; // tata would be set to true or false, whatever toto is.

如果toto是undefined或null以及true，则第一个!将设置为false，第二个将其反转.

The first ! would be set to false if toto is undefined or null and true else, and the second one would invert it.

但是看起来有点奇怪.那么，有没有更清晰的方法呢?

But it looks a little bit odd. So is there a clearer way to do this?

我已经看过

I already looked at this question, but I want to set a value in a variable, not just check it in an if statement.

推荐答案

是的，您始终可以使用以下方法:

Yes, you can always use this:

var tata = Boolean(toto);

这是一些测试:

for (var value of [0, 1, -1, "0", "1", "cat", true, false, undefined, null]) {
    console.log(`Boolean(${typeof value} ${value}) is ${Boolean(value)}`);
}

结果:

Boolean(number 0) is false
Boolean(number 1) is true
Boolean(number -1) is true
Boolean(string 0) is true
Boolean(string 1) is true
Boolean(string cat) is true
Boolean(boolean true) is true
Boolean(boolean false) is false
Boolean(undefined undefined) is false
Boolean(object null) is false

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