code: function(callback, guid) {
  		// If the guid has not been supplied then create a new one.
  		guid = guid || '_hellojs_' + parseInt(Math.random() * 1e12, 10).toString(36);
  
  		// Define the callback function
  		window[guid] = function() {
  			// Trigger the callback
  			try {
  				if (callback.apply(this, arguments)) {
  					delete window[guid];
  				}
  			}
  			catch (e) {
  				console.error(e);
  			}
  		};
  
  		return guid;
  	}
docs: Global Events Attach the callback to the window object Return its unique reference