YUI Scroll Events

yui.scroll.js

YUI.add('scroll', function (Y) {
	var DOC_ELEMENT = Y.config.doc.documentElement,
		WIN = Y.config.win,

		UP = 'up',
		RIGHT = 'right',
		DOWN = 'down',
		LEFT = 'left',

		EDGE = 'edge',
		SCROLL = 'scroll',
		SNAP = 'snap',
		START = 'start';

	function Scroll() {
		var instance = this;

		Scroll.superclass.constructor.apply(instance, arguments);
	}

	Scroll.NAME = SCROLL;
	Scroll.NS = SCROLL;

	Scroll.ATTRS = {
		_timeout: {
			validator: Y.Lang.isNumber,
			value: 250
		}
	};

	Y.extend(Scroll, Y.Plugin.Base, {
		initializer: function (config) {
			var instance = this;

			instance._reset();

			Y.one(instance.get('host')).on(SCROLL, Y.bind(instance._onScroll, instance));
		},

		_onScroll: function (event) {
			var instance = this;

			var lastDetail = instance._lastDetail;

			var detail = {
				scrollDown: WIN.scrollY > lastDetail.scrollY,
				scrollLeft: WIN.scrollX < lastDetail.scrollX,
				scrollRight: WIN.scrollX > lastDetail.scrollX,
				scrollSnapX: WIN.scrollX - instance._maxX,
				scrollSnapY: WIN.scrollY - instance._maxY,
				scrollUp: WIN.scrollY < lastDetail.scrollY,
				scrollX: WIN.scrollX,
				scrollY: WIN.scrollY
			};

			if (detail.scrollUp && !lastDetail.scrollUp) {
				instance.fire(UP + START, detail);
			}

			if (detail.scrollUp) {
				instance.fire(UP, detail);
			}

			if (detail.scrollUp && detail.scrollY == 0) {
				instance.fire(UP + EDGE, detail);
			}

			if (detail.scrollUp && detail.scrollY < 0 && lastDetail.scrollSnapY >= 0) {
				instance.fire(UP + SNAP + START, detail);
			}

			if (detail.scrollUp && detail.scrollY < 0) {
				instance.fire(UP + SNAP, detail);
			}

			if (detail.scrollRight && !lastDetail.scrollRight) {
				instance.fire(RIGHT + START, detail);
			}

			if (detail.scrollRight && detail.scrollSnapX > 0 && lastDetail.scrollSnapX < 1) {
				instance.fire(RIGHT + SNAP + START, detail);
			}

			if (detail.scrollRight) {
				instance.fire(RIGHT, detail);
			}

			if (detail.scrollRight && detail.scrollSnapX == 0) {
				instance.fire(RIGHT + EDGE, detail);
			}

			if (detail.scrollRight && detail.scrollSnapX > 0) {
				instance.fire(RIGHT + SNAP, detail);
			}

			if (detail.scrollDown && !lastDetail.scrollDown) {
				instance.fire(DOWN + START, detail);
			}

			if (detail.scrollDown && detail.scrollSnapY > 0 && lastDetail.scrollSnapY < 1) {
				instance.fire(DOWN + SNAP + START, detail);
			}

			if (detail.scrollDown) {
				instance.fire(DOWN, detail);
			}

			if (detail.scrollDown && detail.scrollSnapY == 0) {
				instance.fire(DOWN + EDGE, detail);
			}

			if (detail.scrollDown && detail.scrollSnapY > 0) {
				instance.fire(DOWN + SNAP, detail);
			}

			if (detail.scrollLeft && !lastDetail.scrollLeft) {
				instance.fire(LEFT + START, detail);
			}

			if (detail.scrollLeft && detail.scrollSnapX > 0 && lastDetail.scrollSnapX < 1) {
				instance.fire(LEFT + SNAP + START, detail);
			}

			if (detail.scrollLeft) {
				instance.fire(LEFT, detail);
			}

			if (detail.scrollLeft && detail.scrollSnapX == 0) {
				instance.fire(LEFT + EDGE, detail);
			}

			if (detail.scrollLeft && detail.scrollSnapX > 0) {
				instance.fire(LEFT + SNAP, detail);
			}

			if (detail.scrollY < 0 || detail.scrollSnapX > 0 || detail.scrollSnapY > 0 || detail.scrollX < 0) {
				instance._reset();
			}

			instance._lastDetail = detail;

			clearTimeout(instance._timeout);

			instance._timeout = setTimeout(instance._reset.bind(instance), instance.get('_timeout'));
		},

		_reset: function () {
			var instance = this;

			instance._maxX = DOC_ELEMENT.scrollWidth - WIN.innerWidth,
			instance._maxY = DOC_ELEMENT.scrollHeight - WIN.innerHeight;

			instance._lastDetail.scrollSnapX = 0;
			instance._lastDetail.scrollSnapY = 0;
		},

		_lastDetail: {},
		_maxX: null,
		_maxY: null,
		_timeout: null
	});

	Y.Plugin.Scroll = Scroll;
}, '0.1.0', {
	requires: ['plugin', 'node']
});