Limiting an input field to only accept numbers

gistfile1.js

function validate(evt) {
  var theEvent = evt || window.event;
	var key = theEvent.keyCode || theEvent.which;
	key = String.fromCharCode( key );
	var regex = /[0-9]|\./;
	if( !regex.test(key) ) {
		theEvent.returnValue = false;
	if(theEvent.preventDefault) theEvent.preventDefault();
	}
}

//<input type="number" name="mynumber" value="" placeholder="number" onkeypress="validate(event)" id="number-0" />