loco.js -- reusable, chainable, multiple, return values

loco.js

var Loco = (function LocoMake () {

	var nadda = {},
		empty = {}
		caboose = null,
		Railcar = function Railcar () {
			this.value = nadda;
			this.deref = this;
		};

	Railcar.prototype.ended = function ended () {
		return this.value === empty;
	};

	Railcar.prototype.motive = function motive () {
		return this.deref.value;
	};

	Railcar.prototype.couple = function couple () {
		var count = arguments.length,
			index = 0,
			before = this,
			after = null,
			temp = null;

		for (index = 0; index < count; index++) {
			after = arguments[index];
			temp = after.deref;
			after.deref = before.deref;
			before.deref = temp;
			before = after;
		}

		return after;
	};

	Railcar.prototype.motion = function motion (skip) {
		var deref = null,
			result = this;

		skip = (skip === void 0) ? 0 : skip;

		do {
			if (this.ended()) {
				result = null;
				break;
			}
			deref = this.deref;
			this.deref = deref.deref;
			deref.repool();
		} while (skip === null || skip-- > 0);

		return result;
	};

	Railcar.prototype.derail = function derail (skip) {
		var deref = this.deref,
			result = deref.value;

		skip = (skip === void 0) ? 0 : skip;

		do {
			deref = this.deref;
			result = deref.value;
			if (!this.motion(0) ||
				result === nadda) {
				result = null;
			}
		} while (skip === null || skip-- > 0);

		return result;
	};

	Railcar.prototype.repool = function repool () {
		if (this.value !== empty) {
			this.value = empty;
			this.deref = caboose;
			caboose = this;
		}
	};

	var unpool = function unpool () {
		var result = null;
		if (caboose) {
			result = caboose;
			result.value = nadda;
			result.deref = result;
			caboose = caboose.deref;
		} else {
			result = new Railcar();
		}
		return result;
	};

	return function Loco () {
		var count = arguments.length,
			index = 0,
			before = null,
			after = null,
			first = null;

		if (count) {
			first = after = before = unpool();
			before.value = arguments[0];
			for (index = 1; index < count; index++) {
				after = unpool();
				after.value = arguments[index];
				before.deref = after;
				before = after;
			}
			before.deref = first;
		}

		return before;
	};

}) ();