Enqueue a task for nextTick in many environments

soon.js

soon = (function() {
	var enqueueTask;

	if(typeof process != 'undefined' && typeof process.nextTick == 'function') {
		// Node nextTick
		enqueueTask = process.nextTick;

	} else if (typeof setImmediate == 'function') {
		// setImmediate for new IE
		enqueueTask = setImmediate;

	} else if (typeof MessageChannel != 'undefined') {
		// modern browsers
		// http://www.nonblocking.io/2011/06/windownexttick.html
		var channel, head, tail;

		channel = new MessageChannel();

		// task list
		head = {};
		tail = head;

		channel.port1.onmessage = function () {
			var next = head.next;
			var task = next.task;
			head = next;
			task();
		};

		enqueueTask = function (task) {
			tail = tail.next = {task: task};
			channel.port2.postMessage();
		};

	} else {
		// Fallback to setTimeout
		enqueueTask = function(func) {
			setTimeout(func, 0);
		}
	}

	return enqueueTask;
        
})();