JavaScript中isNaN函数方法是返回一个 Boolean 值,指明提供的值是否是保留值 NaN (不是数字)。 使用方法: isNaN(numValue) 其中必选项 numvalue 参数为要检查是否为 NAN 的值。 如果值是 NaN, 那么isNaN 函数返回 true ,否则返回 false 。 使用这个函数的典型情况是检查 parseInt 和 parseFloat 方法的返回值。
使用內建isNaN()函式檢查 JavaScript 中的值是否為NaN 執行此檢查的最有用的方法之一是使用標準庫方法isNaN()。如果你給它的值是NaN,那麼這個函式的返回值將是true。這是一個如何在程式碼中使用它的示例: letmyvar_1='dog';letmyvar_2='2';console.log(isNaN(myvar_1));console.log(isNaN(myvar_2)...
Check if a value is NaN: isNaN(123); isNaN(-1.23); isNaN(5-2); isNaN(0); Try it Yourself » isNaN('123'); isNaN('Hello'); isNaN('2005/12/12'); Try it Yourself » More examples below. Description In JavaScriptNaNis short for "Not-a-Number". ...
The Object constructor creates an object wrapper for the given value. If the value is null or undefined, it will create and return an empty object, otherwise, it will return an object of a type that corresponds to the given value. If the value is an object already, it will return the ...
NaN doesn't check if the passed value is infinite or not - it checks if the input val evaluates into a "Type: Number" end-result. Because isNaN(string) is accepted, so the: isNaN("3.14") //false (which means true, the given token is duck converted into a type Number successfully...
constarray=[1,2,3,4,5];constvalueToCheck=3;if(array.includes(valueToCheck)){console.log("Value exists in array.");}else{console.log("Value does not exist in array.");} 使用jQuery 的$.inArray()方法: 代码语言:javascript 复制
Introducing isNaN NaNis a special value in Javascript, which stands for "Not a Number". If you try to parse a text string in Javascript as anint, you'll get NaN: letx=parseInt("hello")// Returns NaN NaNin itself is kind of confusing, and you don't always get the results you woul...
Number.isNaN=Number.isNaN||function(value){returntypeofvalue==="number"&&isNaN(value);} 而Number.isFinite等价于: 代码语言:javascript 复制 if(Number.isFinite===undefined)Number.isFinite=function(value){returntypeofvalue==='number'&&isFinite(value);} ...
//code to check if a value exists in an array using javascript indexOf var fruits_arr = ['Apple', 'Mango', 'Grapes', 'Orange', 'Fig', 'Cherry']; var string = "Orange"; // Find in Array fruits_arr.indexOf('Tomato'); fruits_arr.indexOf('Grapes'); // Find in String string...
If you'd like to check if a variable is a number, your best bet is to use the Number.isFinite() function. Using the Number.isNaN() Function The standard Number object has an isNaN() method. It takes one argument, and determines if its value is NaN. Since we want to check if a...