来自 isNaN 的MDN文档:

From the MDN docs for isNaN:

与JavaScript中所有其他可能的值不同，不可能 依靠相等运算符(==和===)来确定是否 值是否为NaN，因为NaN == NaN和NaN === NaN都会求值 虚假.因此，必须要有isNaN函数.

Unlike all other possible values in JavaScript, it is not possible to rely on the equality operators (== and ===) to determine whether a value is NaN or not, because both NaN == NaN and NaN === NaN evaluate to false. Hence, the necessity of an isNaN function.

改用 isNaN .