使用js自带全局函数isNaN(), isNaN()返回一个Boolean值,如下 : var c=”hello”; //字符串 isNaN(c); //返回一个true; var c=10; //数字 isNaN(c);//返回一个false 如果以上c为一个空串或是一个空格,isNaN将把c当作数字0来处理,所以检查不严谨。 第二种方法:正则表达式 function ch
="number"){return'It must be number!'// Return an error message}// Check if the number is not zero, is a power of two, and has only one bit set in even positionreturnn!=0&&(n&(n-1))==0&&(n&0xAAAAAAAA)==0;}
// program to check if the number is even or odd// take input from the userconstnumber = prompt("Enter a number: ");// ternary operatorconstresult = (number %2==0) ?"even":"odd";// display the resultconsole.log(`The number is${result}.`); Run Code Output Enter a number: 5...
Use parseFloat() to try to convert n to a number. Use !Number.isNaN() to check if num is a number.
/* * 校验是否为空(null/空串) */ var checkNull = function(str){ if(str == null || str == ""){ return false; } return true; } 1.2、校验是否为纯数字 /* * 校验是否为纯数字 * js的isNaN函数 */ var checkNum = function(num){ ...
如上可以看到,通过调用isArray 方法也可以判断是否为数组的列子。 我们现在可以看到,对于第二点和第三点分别使用instanceof方法和constructor属性貌似都可以来判断是否为数组了,但是也有列外情况,比如在跨框架iframe的时候使用页面中的数组时,会失败,因为在不同的框架iframe中,创建的数组是不会相互共享其prototype属性的...
Determining the sign of a number is super easy now with ES6's Math.sign! It will indicate whether the number is positive, negative or zero...
log(i) //returns error Listing 3-6When Creating a Variable Using the var Keyword Inside a Function, the Execution Context is Local to the Function 当处理变量时,在var上使用let将确保变量只存在于你创建的代码块中。变量表现不同的原因是因为变量提升。下一节将更详细地解释吊装。
See the Pen JavaScript: Check from three given integers that whether a number is greater than or equal to 20 and less than one of the others - basic-ex-44 by w3resource (@w3resource) on CodePen.Flowchart: ES6 Version:// Define a function named lessby20_others using arrow function ...
Number.isNaN(5/"5")// trueNumber.isNaN(parseFloat("hello"))// true EitherNumber.isNaNorisNaNwill solve most of your number-checking needs, but there is one additional way to check if something is a number in Javascript Using isInteger and isSafeInteger to check a number in Javascript ...