In JS to determine whether the variable is a digital isNaN function

isNaN function

isNaN (expression:object): Boolean

Common validation numbers

The code is as follows	Copy Code
document.write (isNaN (123));//false document.write (isNaN ( -1.23));//false document.write (isNaN (5-2));//false document.write (isNaN (0));//false document.write (isNaN ("Hello"));//true document.write (isNaN ("2005/12/12"));//true document.write (isNaN ("6/2"));//true document.write (isNaN ("3"));//false

Examples of applications

code is as follows	copy code
if ( isNaN (Document.login.imgcode.value)) {    alert (' Captcha must be a number! ')    document.login.imgcode.focus ();    return false; } If (!isnum (document.getElementById ("Prjsum"). Value) {     alert ("Cost can only be a number");     document.getElementById ("Prjsum"). focus ();     return false;        }