如果有什么的Equals为NaN

Question

是否可以写类似：

if(* === NaN){ 
      this = 0; 
     }; 

我试图做的是赶上计算为NaN的所有数学或变量，并使其等于0，我可以写如果每次数学计算的语句都一样，但它会很混乱，我希望有这样一个简单的解决方案。

Answer 1

我不这么认为，因为据我所知，什么都不等于NaN。然而，你可以利用这一点，并做到这一点：

if(* !== *){ 
     //code when * is NaN 
    }; 

而且只有NaN将符合条件。 I read this is safer than just to use isNaN()。

Answer 2

你可以做这样的事情

function convertIfNaN (x) { 
    if (isNaN(x)) 
     return 0; 
    else 
     return x; 
} 

Answer 3

可以使用isNaN功能，像这样：

if (isNaN(x)) { 
    // do something 
} 

内置的isNaN功能只检查是否值可强制转换为一个数。您也可以编写自己的函数来简单地检查值“南”，例如：

function isNaN(x){ 
    return x !== x; 
} 

Answer 4

我会继续前进，张贴在这里计数器对策：不要使用全球isNaN()功能的JavaScript。它的命名非常糟糕，因为它的工作方式与其签名不符。如果用作数学表达式的一部分，它实际上会检查您在中传递的参数是否将转换为NaN。或者更简单地说：如果您尝试将参数转换为数字，它是否可以转换。下面是一些例子来说明这一点：

console.log("A number: ", isNaN(42))// it is not "not a number" 
 
console.log("A mathematical concept: ", isNaN(Infinity)) // not a "not a number" still 
 
console.log("NaN: ", isNaN(NaN))// naturally, NaN is not a number 
 
console.log("A garbage operation: ", isNaN(42 * "watermelon"))// its meaningless mathematically, so it produces NaN as a result 
 
console.log("A letter: ", isNaN("a"))// clearly not an NaN value, but if converted to a number, it would be 
 
console.log("An object: ", isNaN({}))// same as above 
 

 
//entering some more bizarre territory 
 
console.log("An empty string: ", isNaN("")) //really? Yes - it will be converted to a zero, hence it is actually a number 
 
console.log("An empty array: ", isNaN([])) //an empty array converts to an empty string first, then to a zero 
 
console.log("An array with values: ", isNaN(["a", "b", "c"])) //nope, can't convert to a number 
 
console.log("Another array with values: ", isNaN([1, 2, 3])) //neither can this 
 
console.log("An array with a single value: ", isNaN([1])) //of course this can...because it's a SINGLE numeric value in the array

等等等等。这种行为并不是不可预测的，但它绝对不是你猜到的，也就是说你会注意到isNaN在告诉你传递的参数是否为实际上是NaN做得非常糟糕。

相反，使用Number.isNaN() function它给你正确的结果

console.log("A number: ", Number.isNaN(42)) 
 
console.log("A mathematical concept: ", Number.isNaN(Infinity)) 
 
console.log("A letter: ", Number.isNaN("a")) 
 
console.log("An object: ", Number.isNaN({})) 
 
console.log("An empty string: ", Number.isNaN("")) 
 
console.log("An empty array: ", Number.isNaN([])) 
 
console.log("An array with values: ", Number.isNaN([1, 2, 3])) 
 

 
console.log("NaN: ", Number.isNaN(NaN))