Getting keycode values in Javascript

I've had to work with getting user input values based off of the keycode from the event a few times, and figured I'd throw together some of that functionality in case anyone else is wrestling with this. Below is a simple "keycode" object that has a few utility functions, and maps of values to keycodes.

keycode = {

	getKeyCode : function(e) {
		var keycode = null;
		if(window.event) {
			keycode = window.event.keyCode;
		}else if(e) {
			keycode = e.which;
		}
		return keycode;
	},

	getKeyCodeValue : function(keyCode, shiftKey) {
		shiftKey = shiftKey || false;
		var value = null;
		if(shiftKey === true) {
			value = this.modifiedByShift[keyCode];
		}else {
			value = this.keyCodeMap[keyCode];
		}
		return value;
	},

	getValueByEvent : function(e) {
		return this.getKeyCodeValue(this.getKeyCode(e), e.shiftKey);
	},

	keyCodeMap : {
		8:"backspace", 9:"tab", 13:"return", 16:"shift", 17:"ctrl", 18:"alt", 19:"pausebreak", 20:"capslock", 27:"escape", 32:" ", 33:"pageup",
		34:"pagedown", 35:"end", 36:"home", 37:"left", 38:"up", 39:"right", 40:"down", 43:"+", 44:"printscreen", 45:"insert", 46:"delete",
		48:"0", 49:"1", 50:"2", 51:"3", 52:"4", 53:"5", 54:"6", 55:"7", 56:"8", 57:"9", 59:";",
		61:"=", 65:"a", 66:"b", 67:"c", 68:"d", 69:"e", 70:"f", 71:"g", 72:"h", 73:"i", 74:"j", 75:"k", 76:"l",
		77:"m", 78:"n", 79:"o", 80:"p", 81:"q", 82:"r", 83:"s", 84:"t", 85:"u", 86:"v", 87:"w", 88:"x", 89:"y", 90:"z",
		96:"0", 97:"1", 98:"2", 99:"3", 100:"4", 101:"5", 102:"6", 103:"7", 104:"8", 105:"9",
		106: "*", 107:"+", 109:"-", 110:".", 111: "/",
		112:"f1", 113:"f2", 114:"f3", 115:"f4", 116:"f5", 117:"f6", 118:"f7", 119:"f8", 120:"f9", 121:"f10", 122:"f11", 123:"f12",
		144:"numlock", 145:"scrolllock", 186:";", 187:"=", 188:",", 189:"-", 190:".", 191:"/", 192:"`", 219:"[", 220:"\\", 221:"]", 222:"'"
	},

	modifiedByShift : {
		192:"~", 48:")", 49:"!", 50:"@", 51:"#", 52:"$", 53:"%", 54:"^", 55:"&", 56:"*", 57:"(", 109:"_", 61:"+",
		219:"{", 221:"}", 220:"|", 59:":", 222:"\"", 188:"<", 189:">", 191:"?",
		96:"insert", 97:"end", 98:"down", 99:"pagedown", 100:"left", 102:"right", 103:"home", 104:"up", 105:"pageup"
	}

};

Typically, you would have an event listener on an input that would call keycode.getValueByEvent(). You would have to pass in the event, (which is by default the first parameter passed into your event listener function). This code handles the shift key modifier and the value that results from using it.