Publish/Subscribe singleton in JavaScript

pubsub.js

/**
 * Singleton publish/subscribe hub.
 */
module.exports = (function() {

    const channel = {};
    const noset = new Set();

    return {
        publish: (name,data) => {
            (channel[name] || noset).forEach( fun => { fun(data); } )
        },
        subscribe: (name,fun) => {
            if ( ! channel[name] ) {
                channel[name] = new Set();
            }
            channel[name].add(fun);
        },
        unsubscribe: (name,fun) => {
            (channel[name] || noset).delete(fun);
        }
    };

})();