gistfile1.js

/**
 * This method is used to scroll a bit closer to the top of the window. As long as the top
 * hasn't been reached the method will call itself at the next animation frame.
 */
_animationLoop: function() {
	var self = this;

	// Perform a step of the animation to go to the top of the window
	window.scrollTo(0, this._easeOutCubic(this._iteration, this._scrollPosition, -this._scrollPosition, this._maxIterations));
	// Increase the iteration counter
	this._iteration++;

	// As long as we haven't gone through the max number of iterations we will have to schedule
	// the next part of the animation
	if (this._iteration <= this._maxIterations) {
		// We're not there yet, request a new animation frame to move a little closer to the top
		requestAnimationFrame(function() {
			self._animationLoop();
		});
	}
},

/**
 * The click handler for the element which will initiate the scroll to top.
 */
_buttonClickHandler: function(event) {
	// We need to remember at which scroll position the document is before we start the
	// animation. We need this value as a constant during the animation.
	this._scrollPosition = this._getScrollPosition();
	// Reset the iteration count
	this._iteration = 0;
	// Start the animation
	this._animationLoop();
},