gistfile1.js

function Animation() {
	this.startTime = null;
	this.endTime = null;
	this.duration = null;
	this.ease = null;
	this.apply = null;

	var self = this;
	this._resolve = null;
	this._promise = new Promise(function(resolve) {
		self._resolve = resolve;
	});
}

Animation.prototype.then = function(fn) {
	return this._promise.then(fn);
}

Animation.prototype.complete = function() {
	this._resolve();
}