setImmediate.js

/** @type {function((Function|string), ...*):number} */
var setImmediate = window.setImmediate || ( function() {

	var id = Math.random();
	var queue = [];

	var FunctionCall = Function.prototype.call;
	
	window.addEventListener( 'message', function(event) {

		if ( event.data != id ) return;

		var q = queue.splice( 0 );
		while ( q.length ) {
			FunctionCall.apply( FunctionCall, q.shift() );
		}

	} );

	return function() {
		if ( !queue.length ) {
			window.postMessage( id, '*' );
		}
		queue.push( arguments );
	};

}() );