Rough snippet of a page-wide key press listener

keyboard-listener.js

function _keyEventWasDataEntry (e)
{
	var key = e.charCode,
	    keychar = String.fromCharCode(key);

	// Return false if key was;
	// 9 tab
	// 8 backspace
	// 16 shift
	// 17 control
	// 18 alt
	// 91 apple command
	// 35 end
	// 36 home
	// 37 left
	// 39 right
	// 38 up
	// 40 down
	// 13 enter
	// ...or the alt or control keys were down
	return !(/^(9|8|16|17|18|91|35|36|37|39|38|40|13)$/.test(key) || e.ctrlKey || e.altKey);
}

// bind behaviours
$('body').delegate('input:text', 'keypress', function(e)
{
	// if user is navigating and not entering data
	if (!_keyEventWasDataEntry(e))
	{
		// allow navigation and quit
		return;
	}

	// if they're entering characters other than numbers and the decimal point
	if (String.fromCharCode(e.charCode).search(/[^0-9\.]/) !== -1)
	{
		// block entry and quit
		return e.preventDefault();
	}
	
	console.log(String.fromCharCode(e.charCode));
});