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 checkNum(input...
halfNum =parseInt(halfNum);// check if number is divisible by 2,// if yes then its not a prime number.if(num%2===0){returnfalse; }do{// if number is divisible by its half value,// if yes, than its not prime numberif(num%halfNum ===0){returnfalse; } }while(--halfNum >...
/* * 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){ ...
// program to check if the number is even or odd // take input from the user const number = prompt("Enter a number: "); //check if the number is even if(number % 2 == 0) { console.log("The number is even."); } // if the number is odd else { console.log("The number...
Therefore, when you check inside (isEven % 2 === 0) it ends up always being false because isEven is NaN. Which will always return false. Instead, using your parameter number is the correct solution. var isEven = function(number) { if (number % 2 === 0) { return true; } else {...
if (Math.sign(number) > 0) { // Positive } else { // Negative } Indeed, if you're just checking the boolean status, then I'd just use the comparative operator instead of using Math.sign. But where Math.sign shines is it returns a number value. This means you can do ...
Check if a number is in ranges values contained in an array of objects Ask Question Asked 2 years ago Modified 2 years ago Viewed 259 times 2 i have an array with couple of values like : let myvar = 17 let myarray = [ { start: 1, end: 10 }, { start: 15, end:...
(input);// increase the number of guessesguesses++;// check input number with the secret number// provide hint if neededif(number> secretNumber) {hint =', and less than '+number;}elseif(number< secretNumber) {hint ...
function CheckMyForm() { var txt = myform.mytext.value; if(checknumber(txt)) { alert("只允许输入数字!"); return false; } return true; } function checknumber(String) { var Letters = "1234567890"; var i; var c; for( i = 0; i < String.length; i ++ ) ...
NaN 是 "Not-a-Number" 的简写,字面上翻译为不是一个数字。在JavaScript 中,NaN 是一个不合法的数字。 Number.isNaN() 方法用于判断传递的值是否为 NaN,并且检查其类型是否为 Number,如果值为 NaN 且类型为 Number,则返回 true,否则返回 false。在...