JavaScript function for annotating other JavaScript

annotation.js

function annotate(fnToAnnotate) {
	// already annotation aware, use the original annotation chain
	if (fnToAnnotate.by) {
		return fnToAnnotate;
	}

	var aAnnotationChain = [fnToAnnotate];

	function applyChainFunctions(fn) {
		fn.by = function(fnAnnotation, arg1, /*...*/ argN) {
			var fnToAnnotate = aAnnotationChain[aAnnotationChain.length - 1],
				fnExecutedAnnotation = function () {
					/*
					 Replace the annotation function in the args list,
					 with the function to annotate. This is a nice little hack
					 to allow us to call the annotation function using apply, passing
					 the function to annotate as the first argument, followed by
					 all the other arguments that were originally passed to ``by``.
					 */
					arguments[0] = fnToAnnotate;
					return fnAnnotation.apply(this, arguments);
				}.apply(this, arguments);

			aAnnotationChain.push(fnExecutedAnnotation);
			return applyChainFunctions(fnExecutedAnnotation);
		};

		return fn;
	}

	return applyChainFunctions(fnToAnnotate);
}