How to force a user to only enter numbers into a text field using JavaScript

Add the following JavaScript function to your HTML page

 
	function isNumberKey(evt)
	{
	     var charCode = (evt.which) ? evt.which : event.keyCode
	     if (charCode > 31 && (charCode < 48 || charCode > 57))
	        return false;
 
	     return true;
	}

The above function checks the input of the user and then returns false if no number has been entered and true if a number has been entered

Then in your textfield HTML code add the following

onkeypress="return isNumberKey(event)"

This will check for a number on every key press from the user

<input type="text" onkeypress="return isNumberKey(event)"  name="number" />