Simple PubSub service file

index.js

import { pubSub } from '../../services/pubsub.service';

//subscribe the event for  pageloader to listen the event
pubSub.subscribe('pageloader', (event) => {
    if (event.show) {
        this.setState({
            isLoading: true
        });
    } else {
        this.setState({
            isLoading: false
        });
    }
});

//publish the event from another file or other soruce event
pubSub.publish('pageloader', {
    show: false
});

pubsub.service.js

let PubSub = function() {
    this.pubSubHash = {};
};

PubSub.prototype.subscribe = function(eventName, eventFn) {
    if (!this.pubSubHash[eventName]) {
        this.pubSubHash[eventName] = [];
    }
    this.pubSubHash[eventName].push(eventFn);
};

PubSub.prototype.publish = function(eventName, eventData) {
    if(this.pubSubHash[eventName]) {
        this.pubSubHash[eventName].forEach(eventFn => {
            eventFn(eventData);
        });
    }
};

export const pubSub = new PubSub();