Simple Pub/Sub

pubsub.js

!function () {
  var channels = {};

  this.subscribe = function (channel, subscription) {
    if (!channels[channel]) channels[channel] = [];
    channels[channel].push(subscription);
  };

  this.publish = function (channel) {
    if (!channels[channel]) return;
    var args = [].slice.call(arguments, 1);
    for (var i = 0, l = channels[channel].length; i < l; i++) {
      channels[channel][i].apply(this, args);
    }
  };
}.call(this);

usage.js

subscribe('foo', function (a, b) {
  console.log(a, b);
});

publish('foo', 1, 2);

if statements require a variable to be instanced, the ternary solves that. your personal quip about the (||) is better than mine and simpler, I was simplifying the code to not instance variables.

The errors were not checking variables, that is up to the creator I suppose, you can exclude it, just a simple "protection" layer.