Angular Keystroke Combo Service

shortcuts.js

'use strict';

angular.module('MyApp')
    .service('Shortcuts', function Shortcuts() {

        var _subscribers = {},
            _keystrokes = [];

        var processKeyStrokes = function processKeyStrokes(keystrokes) {
            // Rebuild the hash, this is probably the quickest way to find our subscribers
            var keystrokeString = keystrokes.join('');

            // Check to see whether the keystroke hash exists in our subscribers list and check the length too
            if (typeof _subscribers[keystrokeString] != 'undefined' && _subscribers[keystrokeString].length > 0) {

                // Loop through the subscribers for this keystroke hash...
                for (var i = 0, j = _subscribers[keystrokeString].length; i < j; i += 1) {
                    // ... and call them :D
                    _subscribers[keystrokeString][i].call(null, keystrokes);
                }
            }

        }

        window.onkeydown = function listentokeyevents(event) {


            // If the keystrokes are empty, listen for a modifier, normally control
            if (_keystrokes.length < 1) {

                if (event.ctrlKey || event.altKey || event.metaKey || event.shiftKey) {
                    _keystrokes.push(event.keyCode);
                }

                return;
            }

            // Else start building the keystrokes
            if (!~_keystrokes.indexOf(event.keyCode)) {
                _keystrokes.push(event.keyCode);
            }

        };

        window.onkeyup = function stoplisteningtokeyevents(event) {
            // Process the keystrokes
            processKeyStrokes(_keystrokes);

            // Clear the keystroke history
            _keystrokes = [];

        };

        return {
            /**
             * Subscribes your callback to an array of keystrokes
             * @param  {[type]}   keystrokes An array of keystrokes starting with a modifier i.e. Shortcuts.subscribe([17, 78], fn) for Ctrl + N
             * @param  {Function} callback   The callback method for the subscriber
             */
            subscribe: function(keystrokes, callback) {

                // Makes sense to use a hash of the keystrokes here, if we have to search through an array for every subscriber it might get messy!
                var keystrokeString = keystrokes.join('');

                if (typeof _subscribers[keystrokeString] == 'undefined') {
                    _subscribers[keystrokeString] = [];
                }

                _subscribers[keystrokeString].push(callback);
            },
            /**
             * Unsubscribes a callback from all keystroke listeners
             * @param  {Function} callback [description]
             * @return {[type]}            [description]
             */
            unsubscribe: function(callback) {
                // Loop through all of the subscribers
                for (var keystrokeString in _subscribers) {

                    // Loop through the keystroke subscribers
                    for (var i = 0, j = keystrokeString.length; i < j; i += 1) {
                        // Find the callback
                        if (angular.equals(keystrokeString[i], callback)) {
                            // Delete that bugger
                            delete keystrokeString[i];
                        }
                    }
                }
            }
        }

    });