Javascript - validation, numbers only


I'm trying to get my login form to only validate if only numbers were inputted. I can it to work if the input is only digits, but when i type any characters after a number, it will still validate etc. 12akf will work. 1am will work. How can i get past this?

Part of the Login

<form name="myForm">
    <label for="firstname">Age: </label>
    <input name="num" type="text" id="username" size="1">
    <input type="submit" value="Login" onclick="return validateForm()">

function validateForm()

    var z = document.forms["myForm"]["num"].value;
        alert("Please only enter numeric characters only for your Age! (Allowed input:0-9)")

This question is tagged with javascript validation numbers

~ Asked on 2012-05-23 05:05:23

The Best Answer is


Match against /^\d+$/. $ means "end of line", so any non-digit characters after the initial run of digits will cause the match to fail.


RobG wisely suggests the more succinct /\D/.test(z). This operation tests the inverse of what you want. It returns true if the input has any non-numeric characters.

Simply omit the negating ! and use if(/\D/.test(z)).

~ Answered on 2012-05-23 05:06:19


here is how to validate the input to only accept numbers this will accept numbers like 123123123.41212313

<input type="text" 
onkeypress="if ( isNaN(this.value + String.fromCharCode(event.keyCode) )) return false;"

and this will not accept entering the dot (.), so it will only accept integers

<input type="text" 
onkeypress="if ( isNaN( String.fromCharCode(event.keyCode) )) return false;"

this way you will not permit the user to input anything but numbers

~ Answered on 2012-10-17 05:57:23

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