messageBus.js

// Prompt: https://gist.github.com/tim-hr/697af278700fcf12014eb36d932ad7c4

var messageBus = {
  subscribers: [],
  subscribe: function(payload) {
    this.subscribers.push(payload);
  },
  publish: function(payload) {
    this.subscribers.forEach(function(sub){
      if (validTopic(payload.topic, sub.topic) && payload.channel === sub.channel) {
        sub.callback(payload.data);
      }
    });
  },
};

var validTopic = function(pubTopic, subTopic) {
  if (subTopic[subTopic.length - 1] === '*'){
    var subTopicPrefix = subTopic.slice(0, -1);
    var pubTopicPrefix = pubTopic.slice(0, subTopic.length - 1);
    if (pubTopicPrefix === subTopicPrefix) {
      return true;
    }
  } else if (subTopic === pubTopic) {
    return true;
  } else {
    return false;
  }
};

// Subscriber subscribes with wildcarding
messageBus.subscribe({
  channel: 'commerce',
  topic: 'order_*',
  callback: function(payload) {
    // do something with the payload
    console.log(payload);
  }
});

// Publisher publishes as normal (no wildcarding on this side)
messageBus.publish({
  channel: 'commerce',
  topic: 'order_started',
  data: {
    user_id: '4273984723428'
  }
});

// The above subscriber receives this message.
messageBus.publish({
  channel: 'commerce',
  topic: 'order_complete',
  data: {
    plan_level: 'GOLD',
    user_id: '4273984723428'
  }
});