@textback/notification-widget/src/sdk/events/observer.js

TODO: Give a short introduction of your project. Let this section explain the objectives or the motivation behind this project.

import assign from 'lodash/assign';

const EVENTS = {
    WIDGET_INIT: 'widget.init',
    SUBSCRIBE_START: 'subscribe.start',
};

const _handlers = {};

window.TextBack = window.TextBack || {};
window.TextBack.Observer = window.TextBack.Observer || {
    on(eventName, fn) {
        if (!_handlers[eventName]) {
            _handlers[eventName] = [ fn ];
        } else {
            _handlers[eventName].push(fn);
        }

        return () => {
            const fnIndex = _handlers[eventName].indexOf(fn);
            if (fnIndex !== -1) {
                _handlers[eventName].splice(fnIndex, 1);
            }
        };
    },

    trigger(eventName, data) {
        if (_handlers[eventName]) {
            const eventData = assign({}, data, { type: eventName });
            setTimeout(() => {
                _handlers[eventName].forEach(handler => {
                    try {
                        handler(eventData)
                    } catch (err) {
                        console.error(`Error occuired while executing event handler on event ${eventName}`, err);
                    }
                });
            }, 0);
            
        }
    }
};

const Observer = window.TextBack.Observer;

export { Observer, EVENTS };