在JS中，“==”符号不检查变量的类型。因此，“0”= 0 = false(在JS中为0 = false)，在这种情况下将返回true，但如果使用“===”，结果将为false。

当你使用"if"时，在以下情况下它将是"false":

[0, false, '', null, undefined, NaN] // null = undefined, 0 = false

So

if("0") = if( ("0" !== 0) && ("0" !== false) && ("0" !== "") && ("0" !== null) && ("0" !== undefined) && ("0" !== NaN) )
        = if(true && true && true && true && true && true)
        = if(true)

显示问题的表格:

和= =

这个故事的寓意使用===

表生成credit: https://github.com/dorey/JavaScript-Equality-Table

0周围的引号使它成为一个字符串，它的值为true。

删除引号，它应该工作。

if (0) console.log("ha") 

==相等运算符在将参数转换为数字后求值。 因此字符串0" 0"被转换为数字数据类型，布尔值false被转换为数字0。 所以

"0" == false // true

同样适用于'

False == "0" //true

===严格的相等性检查使用原始数据类型计算参数

"0" === false // false，因为"0"是字符串，false是布尔值

同样适用于

False === "0" // False

In

if（“0”） console.log（“ha”）;

String "0"不与任何参数进行比较，并且String在与任何参数进行比较之前都是真值。 就像

if (true) console.log (" ha ");

But

If (0) console.log("ha");//空控制台行，因为0是假的

`

The "if" expression tests for truthiness, while the double-equal tests for type-independent equivalency. A string is always truthy, as others here have pointed out. If the double-equal were testing both of its operands for truthiness and then comparing the results, then you'd get the outcome you were intuitively assuming, i.e. ("0" == true) === true. As Doug Crockford says in his excellent JavaScript: the Good Parts, "the rules by which [== coerces the types of its operands] are complicated and unmemorable.... The lack of transitivity is alarming." It suffices to say that one of the operands is type-coerced to match the other, and that "0" ends up being interpreted as a numeric zero, which is in turn equivalent to false when coerced to boolean (or false is equivalent to zero when coerced to a number).

// I usually do this:

x = "0" ;

if (!!+x) console.log('I am true');
else      console.log('I am false');

// Essentially converting string to integer and then boolean.