LanguagesJavaScriptJavaScripts: Prevent a User from Entering Non-numeric Characters

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This article was contributed by
Bart T. McDonough.

Environment: IE 4.0 and above

Function Name: “CheckNumeric()”

This Javascript function prevents a user from being able to enter non-numeric
data into a text field in an HTML form. When a user types data into a text
field that uses this function, only numeric characters which are typed actually
appear in the field. Any other characters are ignored and do not appear. It is
a useful tool if you’re looking for a simple way to ensure you have numeric
data without having to write a validation routine.

To use this function, simply call it as an “onkeypress()” event handler in your <INPUT>
tag in your HTML code. To see how this is done, view or download the source code below.

This function does not require any input parameters and does not output any return

function CheckNumeric()
// Get ASCII value of key that user pressed
var key = window.event.keyCode;

// Was key that was pressed a numeric character (0-9)?
if ( key > 47 && key < 58 )
return; // if so, do nothing
window.event.returnValue = null; // otherwise,
// discard character



Download demo project – .97 Kb

Download source – 1.11 Kb


Date Posted: January 31, 2002

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