Question

是否可以编写如下内容：

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

我要做的是捕获计算为NaN的任何数学或变量并使它们等于0.我可以为每次数学运算写出相同的if语句但是它会很混乱我希望那里这是一个简单的解决方案。

Answer 1

我不这么认为，因为据我所知，没有什么比NaN更重要了。但是，您可以利用它并执行：

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

只有NaN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

您可以像这样使用isNaN函数：

<!--[if gte mso 12]>
<td>
    <img src="fallback.jpg">
</td>
<![endif]-->

<!--[if !gte mso 12]><!-- -->
<td>
    <img src="animated.gif">
</td>
<!--<![endif]-->

内置的isNaN函数仅检查值是否可以强制转换为数字。您也可以编写自己的函数来简单地检查值“NaN”，如下所示：

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

Answer 4

我必须继续并在此处发布反对响应：不要在JavaScript中使用全局isNaN()函数。它名称非常糟糕，因为它的工作方式与其签名不符。它实际上会检查您在中传递的参数是否会转换为NaN ，如果用作数学表达式的一部分。或者更简单地说：如果你试图将参数转换为数字，可以转换它。以下是一些例子来说明这一点：

＆＃13;

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

＆＃13;

依此类推。这种行为不是不可预测的，但它肯定不是你猜的那样，即你会注意到通知isNaN在告诉你传入的参数是否实际上是非常糟糕的工作< / em> NaN。

相反，请使用能够提供正确结果的Number.isNaN() function

＆＃13;
＆＃13;
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))
＆＃13;
＆＃13;
＆＃13;

如果任何等于NaN

4 个答案: