pubSubImpl.js

const t = (function () {
    var _listeners = {};
    /**
     * Compare with a new listener handler
     * to make sure we are not adding the same handler
     * @param String EventType
     * @param Function Callback
     * @returns Boolean true if exists false if not
     */
    var _existsHandler = function (eventType, cb) {
        return _getHandlerIndex(eventType, cb) > -1 ? true : false;
        //return Object.values(_listeners).some(ls => ls.some(l => l.cb === cb));
    };
    /**
     * Get index of the handler on a specified eventType
     * @param String EventType
     * @param Function Callback
     * @returns -1 if element does not exist OR > -1 if it does
     */
    var _getHandlerIndex = function (eventType, cb) {
        return _listeners[eventType].findIndex(function (l, n) { return l.cb === cb; });
    };
    /**
     * addListener
     * Allow listeners to subscribe for a specific event type
     * @param string eventType
     * @param ListenerParams <OPTIONAL> Listener options, ATM only includes priority
     * @param function callback
     * @returns Listener
     */
    var subscribe = function (eventType, params, cb) {
        if (params === void 0) { params = { priority: 0 }; }
        var newListener = {
            eventType: eventType,
            cb: cb,
            priority: params && params.priority ? params.priority : 0
        };
        // Event Type does not exist create a new array
        if (!_listeners[eventType]) {
            _listeners[eventType] = [];
            // Check if callback already on the listeners stack
        }
        else if (_existsHandler(eventType, newListener.cb)) {
            // TODO: Show some error to the user
            return;
        }
        var isInserted = _listeners[eventType].some(function (l, i) {
            // if newListener priority is higher insert at index
            if (newListener.priority > l.priority) {
                _listeners[eventType].splice(i, 0, newListener);
                return true;
            }
        });
        if (!isInserted) {
            _listeners[eventType].push(newListener);
        }
        return newListener;
    };
    var unsubscribe = function (eventType, cb) {
        // If no listener with the associated event Type exists
        if (!_listeners[eventType])
            return;
        var index = _getHandlerIndex(eventType, cb);
        if (index < 0)
            return;
        _listeners[eventType][index] = null;
    };
    /**
     * publish an event to currently subscribed
     * listeners on the eventType
     * @param EventType The data to be published
     * @param data The data to be published
     */
    var publish = function (EventType, data) {
        // If no listeners on the current eventType
        // no need to do stuff
        if (!_listeners[EventType])
            return;
        _listeners[EventType].forEach(function (l) { return l.cb(data); });
    };
    return {
        subscribe: subscribe,
        unsubscribe: unsubscribe,
        publish: publish
    };
})();