tiny-events/lib/index.js

A very tiny EventEmitter implementation for client- and server-side code.

function EventEmitter() {
    this._listeners = {};
}

EventEmitter.prototype.on = function _on(type, listener) {
    if (!Array.isArray(this._listeners[type])) {
        this._listeners[type] = [];
    }

    if (this._listeners[type].indexOf(listener) === -1) {
        this._listeners[type].push(listener);
    }

    return this;
};

EventEmitter.prototype.once = function _once(type, listener) {
    var self = this;

    function __once() {
        for (var args = [], i = 0; i < arguments.length; i += 1) {
            args[i] = arguments[i];
        }

        self.off(type, __once);
        listener.apply(self, args);
    }

    __once.listener = listener;

    return this.on(type, __once);
};

EventEmitter.prototype.off = function _off(type, listener) {
    if (!Array.isArray(this._listeners[type])) {
        return this;
    }

    if (typeof listener === 'undefined') {
        this._listeners[type] = [];
        return this;
    }

    var index = this._listeners[type].indexOf(listener);

    if (index === -1) {
        for (var i = 0; i < this._listeners[type].length; i += 1) {
            if (this._listeners[type][i].listener === listener) {
                index = i;
                break;
            }
        }
    }

    this._listeners[type].splice(index, 1);
    return this;
};

EventEmitter.prototype.emit = function _emit(type) {
    if (!Array.isArray(this._listeners[type])) {
        return this;
    }

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

    this._listeners[type].forEach(function __emit(listener) {
        listener.apply(this, args);
    }, this);

    return this;
};

module.exports.EventEmitter = EventEmitter;