kaiwa/clientapp/modules/wildemitter.js

/*
WildEmitter.js is a slim little event emitter by @henrikjoreteg largely based 
on @visionmedia's Emitter from UI Kit.

Why? I wanted it standalone.

I also wanted support for wildcard emitters like this:

emitter.on('*', function (eventName, other, event, payloads) {
    
});

emitter.on('somenamespace*', function (eventName, payloads) {
    
});

Please note that callbacks triggered by wildcard registered events also get 
the event name as the first argument.
*/
module.exports = WildEmitter;

function WildEmitter() {
    this.callbacks = {};
}

// Listen on the given `event` with `fn`. Store a group name if present.
WildEmitter.prototype.on = function (event, groupName, fn) {
    var hasGroup = (arguments.length === 3),
        group = hasGroup ? arguments[1] : undefined, 
        func = hasGroup ? arguments[2] : arguments[1];
    func._groupName = group;
    (this.callbacks[event] = this.callbacks[event] || []).push(func);
    return this;
};

// Adds an `event` listener that will be invoked a single
// time then automatically removed.
WildEmitter.prototype.once = function (event, groupName, fn) {
    var self = this,
        hasGroup = (arguments.length === 3),
        group = hasGroup ? arguments[1] : undefined, 
        func = hasGroup ? arguments[2] : arguments[1];
    function on() {
        self.off(event, on);
        func.apply(this, arguments);
    }
    this.on(event, group, on);
    return this;
};

// Unbinds an entire group
WildEmitter.prototype.releaseGroup = function (groupName) {
    var item, i, len, handlers;
    for (item in this.callbacks) {
        handlers = this.callbacks[item];
        for (i = 0, len = handlers.length; i < len; i++) {
            if (handlers[i]._groupName === groupName) {
                //console.log('removing');
                // remove it and shorten the array we're looping through
                handlers.splice(i, 1);
                i--;
                len--;
            }
        }
    }
    return this;
};

// Remove the given callback for `event` or all
// registered callbacks.
WildEmitter.prototype.off = function (event, fn) {
    var callbacks = this.callbacks[event],
        i;
    
    if (!callbacks) return this;

    // remove all handlers
    if (arguments.length === 1) {
        delete this.callbacks[event];
        return this;
    }

    // remove specific handler
    i = callbacks.indexOf(fn);
    callbacks.splice(i, 1);
    return this;
};

// Emit `event` with the given args.
// also calls any `*` handlers
WildEmitter.prototype.emit = function (event) {
    var args = [].slice.call(arguments, 1),
        callbacks = this.callbacks[event],
        specialCallbacks = this.getWildcardCallbacks(event),
        i,
        len,
        item;

    if (callbacks) {
        for (i = 0, len = callbacks.length; i < len; ++i) {
            if (callbacks[i]) {
                callbacks[i].apply(this, args);
            } else {
                break;
            }
        }
    }

    if (specialCallbacks) {
        for (i = 0, len = specialCallbacks.length; i < len; ++i) {
            if (specialCallbacks[i]) {
                specialCallbacks[i].apply(this, [event].concat(args));
            } else {
                break;
            }
        }
    }

    return this;
};

// Helper for for finding special wildcard event handlers that match the event
WildEmitter.prototype.getWildcardCallbacks = function (eventName) {
    var item,
        split,
        result = [];

    for (item in this.callbacks) {
        split = item.split('*');
        if (item === '*' || (split.length === 2 && eventName.slice(0, split[1].length) === split[1])) {
            result = result.concat(this.callbacks[item]);
        }
    }
    return result;
};