trigger a function with a given key sequence

keySequenceTrigger.js

/**
* @license License and Terms of Use
*
* Copyright (c) 2013 SignpostMarv
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
* THE SOFTWARE.
*/
/**
* Examples:
keySequenceTrigger(
	'one-time-only',
	function(){
		console.log('KTHXBAI!');
		// keySequenceTrigger calls the trigger function with handler as the
		//	this argument, enabling minimalist removal logic.
		keySequenceTrigger.remove(this);
	}
);
keySequenceTrigger({
	sequence : '↑↑↓↓←→←→ba',
	trigger  : function(){
		console.log('KONAMI CODE!');
	}
});
keySequenceTrigger({
	sequence : '⎈⎇⇑h', // ctrl, alt, shift, h
	trigger  : function(){
		console.log('HIPPOS!');
	}
});
*/

(function(window, undefined){
	'use strict';
	var
		ArrayProt        = window['Array'].prototype,
		callBacks        = {},
		sequenceCounters = {},
		addEvent         = isIn(document, 'addEventListener')
			? function(a,b,c){ a.addEventListener(b, c, false); }
			: function(a,b,c){ a.addEvent(b, c); }
	;
	function isIn(obj, prop){
		return (prop in obj);
	}
	function hasOwn(obj, prop){
		for(var i=1;i<arguments.length;++i){
			if(!obj.hasOwnProperty(prop)){
				return false;
			}
		}
		return true;
	}
	if(!hasOwn(ArrayProt, 'forEach')){
		ArrayProt['forEach'] = function(cb){
			for(var i=0;i<this.length;++i){
				cb(this[i], i, this);
			}
		}
	}

	function sequenceModifier(sequenceIn){
		var
			sequenceOut = sequenceIn,
			replacements = {
				'⇑' : 16, '⇑' : 16, // shift key
				'⎈' : 17, '⎈' : 17, // ctrl key
				'⎇' : 18, '⎇' : 18, // alt key
				'←' : 37, 'â†'  : 37,
				'↑' : 38, '↑' : 38,
				'→' : 39, '→' : 39,
				'↓' : 40, '↓' : 40,
			}
		;
		for(var i in replacements){
			if(hasOwn(replacements, i)){
				sequenceOut = sequenceOut.replace(
					new RegExp(i, 'g'),
					String.fromCharCode(replacements[i])
				);
			}
		}

		return sequenceOut.toLowerCase();
	}

	function keySequenceTrigger(opts){
		// assignment
		var
			self = this,
			sequence, trigger, element, sequenceIn
		;
		if(arguments.length == 0){
			throw new Error('No arguments supplied');
		}else if(arguments.length == 1){
			if(typeof(opts) != 'object'){
				throw new Error('One argument supplied, but not as object!');
			}else{
				sequence   = opts.sequence;
				trigger    = opts.trigger;
				element    = opts.element;
			}
		}else if(arguments.length >= 2){
			sequence = arguments[0];
			trigger  = arguments[1];
			element  = arguments[2]
		}
		element = element || document;

		// validation
		if(typeof(sequence) != 'string'){
			throw new Error('Sequence must be supplied as string!');
		}else if(typeof(trigger) != 'function'){
			throw new Error('Trigger must be supplied as function!');
		}else if(
			!isIn(element, 'addEventListener')
			&& !isIn(element, 'attachEvent')
		){
			throw new Error('Element must support event attachment!');
		}
		sequenceIn = sequence;
		sequence = sequenceModifier(sequence);

		if(!hasOwn(callBacks, sequence)){
			callBacks[sequence] = [];
		}
		if(!hasOwn(sequenceCounters, sequence)){
			sequenceCounters[sequence] = 0;
		}

		var handler = function(){trigger.call(handler)};
		handler.sequenceIn = sequenceIn;
		handler.sequence   = sequence;
		handler.element    = element;

		callBacks[sequence].push(handler);
	}
	keySequenceTrigger.remove = function(){
		var
			removeThese = {}
		;
		for(var i=0;i<arguments.length;++i){
			if(hasOwn(arguments[i], 'sequence')){
				var
					handler = arguments[i],
					sequence = handler.sequence
				;
				if(hasOwn(callBacks, sequence)){
					var pos = callBacks[sequence].indexOf(handler);
					if(pos >= 0){
						if(!hasOwn(removeThese, sequence)){
							removeThese[sequence] = [];
						}
						removeThese[sequence].push(pos);
					}
				}
			}
		}
		for(var sequence in removeThese){
			removeThese[sequence].sort();
			removeThese[sequence].reverse();
			removeThese[sequence].forEach(function(e){
				callBacks[sequence].splice(e, 1);
			});
		}
	}

	function keyEventHandler(e){
		var
			e = e || window.event
		;
		if(e.type == 'down' && (e.keyCode < 37 || e.keyCode > 40)){
			return; // we only want keydown for arrow keys
		}else if(
			(e.keyCode < 65 || e.keyCode > 90) // ignore upper-case
			&& (e.keyCode < 189) // ignore duplicate events
		){
			var
				callThese = []
			;
			for(var i in sequenceCounters){
				if(
					hasOwn(sequenceCounters, i)
					&& hasOwn(callBacks, i) // callback check
				){
					if(e.keyCode == i.charCodeAt(sequenceCounters[i])){
						++sequenceCounters[i];
						if(sequenceCounters[i] >= i.length){
							callBacks[i].forEach(function(f){
								if(e.target == f.element || (f.element == document && e.target == document.body)){
									callThese.push(f);
								}
							});
							sequenceCounters[i] = 0;
						}
					}else{
						sequenceCounters[i] = 0;
					}
				}
			}

			callThese.forEach(function(f){
				f();
			});
		}
	}

	['keypress', 'keydown'].forEach(function(e){
		addEvent(document, e, keyEventHandler);
	});

	window['keySequenceTrigger'] = keySequenceTrigger;
})(window);