JavaScript - check for numbers in a text field

It takes in the value of a textfield, Im trying to have it so if any numbers are in the field then il be able to stop it.

 function hasNumbers(input) {

     var length = input.length;
     var end = 0;

     for (var x = 0; x < length; x++) {
         var char = input.substring(x, 1);
         trueFalse = isNaN(char);
         if (! trueFalse) {

     if (end > 0) {
         return false;

     return true;


You can replace your function with this:

function hasNumbers(input) {
    return /[0-9]/.test(input);

/[0-9]/ constructs a regular expression that matches any numeric character.

Once you have a regex object, you can call test(s) to see if s matches the regex.

Here is more information about the RegExp.test() method.

Here is more info on regular expressions in general.

Here is a fiddle that shows the above code in action.

Here is another fiddle that shows the above function validating a text input.

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