vczero.github.io/meitu/js/lib/events.js

define('lib/events', function (require, exports, module) {
    var eventSplitter = /\s+/;
    function Events() {}
    Events.prototype.on = function (events, callback, context) {
        var cache, event, list;
        if (!callback) return this;

        cache = this.__events || (this.__events = {});
        events = events.split(eventSplitter);

        while (event = events.shift()) {
            list = cache[event] || (cache[event] = []);
            list.push(callback, context);
        }

        return this;
    };

    Events.prototype.once = function (events, callback, context) {
        var that = this;
        var cb = function () {
            that.off(events, cb);
            callback.apply(this, arguments);
        };
        this.on(events, cb, context);
    };
    Events.prototype.off = function (events, callback, context) {
        var cache, event, list, i;
        if (!(cache = this.__events)) return this;
        if (!(events || callback || context)) {
            delete this.__events;
            return this;
        }
        events = events ? events.split(eventSplitter) : keys(cache);

        while (event = events.shift()) {
            list = cache[event];
            if (!list) continue;

            if (!(callback || context)) {
                delete cache[event];
                continue;
            }

            for (i = list.length - 2; i >= 0; i -= 2) {
                if (!(callback && list[i] !== callback ||
                    context && list[i + 1] !== context)) {
                    list.splice(i, 2);
                }
            }
        }

        return this;
    };

    Events.prototype.trigger = function (events) {
        var cache, event, all, list, i, len, rest = [],
            args, returned = true;
        if (!(cache = this.__events)) return this;

        events = events.split(eventSplitter);

        for (i = 1, len = arguments.length; i < len; i++) {
            rest[i - 1] = arguments[i];
        }

        while (event = events.shift()) {
            // Copy callback lists to prevent modification.
            if (all = cache.all) all = all.slice();
            if (list = cache[event]) list = list.slice();

            // Execute event callbacks.
            returned = triggerEvents(list, rest, this) && returned;

            // Execute "all" callbacks.
            returned = triggerEvents(all, [event].concat(rest), this) && returned;
        }

        return returned;
    };

    Events.prototype.emit = Events.prototype.trigger;

    // Mix `Events` to object instance or Class function.
    Events.mixTo = function (receiver) {
        receiver = isFunction(receiver) ? receiver.prototype : receiver;
        var proto = Events.prototype;

        for (var p in proto) {
            if (proto.hasOwnProperty(p)) {
                receiver[p] = proto[p];
            }
        }
    };


    // Helpers
    // -------

    var keys = Object.keys;

    if (!keys) {
        keys = function (o) {
            var result = [];

            for (var name in o) {
                if (o.hasOwnProperty(name)) {
                    result.push(name);
                }
            }
            return result;
        };
    }

    // Execute callbacks
    function triggerEvents(list, args, context) {
        var pass = true;

        if (list) {
            var i = 0,
                l = list.length,
                a1 = args[0],
                a2 = args[1],
                a3 = args[2];
            // call is faster than apply, optimize less than 3 argu
            // http://blog.csdn.net/zhengyinhui100/article/details/7837127
            switch (args.length) {
            case 0:
                for (; i < l; i += 2) {
                    pass = list[i].call(list[i + 1] || context) !== false && pass;
                }
                break;
            case 1:
                for (; i < l; i += 2) {
                    pass = list[i].call(list[i + 1] || context, a1) !== false && pass;
                }
                break;
            case 2:
                for (; i < l; i += 2) {
                    pass = list[i].call(list[i + 1] || context, a1, a2) !== false && pass;
                }
                break;
            case 3:
                for (; i < l; i += 2) {
                    pass = list[i].call(list[i + 1] || context, a1, a2, a3) !== false && pass;
                }
                break;
            default:
                for (; i < l; i += 2) {
                    pass = list[i].apply(list[i + 1] || context, args) !== false && pass;
                }
                break;
            }
        }
        // trigger will return false if one of the callbacks return false
        return pass;
    }

    function isFunction(func) {
        return Object.prototype.toString.call(func) === '[object Function]';
    }

    return Events;
});