Parallax js class

parallax.js

/**
 * Simple parallax helper: calls all registered callbacks with current scroll top as parameter.
 */

var Parallax = (function () {

    var windowWidth = null;
    var windowHeight = null;
    var y = null;
    var y_norm = null;
    var y_norm_to_current = null;
    var current_page = null;
    var max_y = null;
    var max_scroll = null;
    var callbacks = [];
    var bounds = [];
    var resizeTimeout = null;
    var container = null;
    var disabled = null;

    var setup = function (config) {

        var defaults = {
            selector: '.parallax-page'
        };

        config = $.extend(defaults, config);

        if (!config.hasOwnProperty('container')) {
            config.container = window;
        }

        container = config.container;

        windowWidth = $(window).width();
        windowHeight = $(window).height();

        max_y = $(config.container).outerHeight();
        max_scroll = $(config.container).outerHeight() - $(window).height();

        bounds[0] = 0;

        $(config.selector)
            .each(function (i) {
                bounds[i+1] = bounds[i] + $(this).outerHeight();
            });

        // console.log('setup done');
    };

    var runCallbacks = function () {
        $.each(callbacks, function (e) {
            this(y, y_norm, y_norm_to_current, windowWidth, windowHeight);
        });
    };

    var update = function (yp) {

        if (disabled) {
            return;
        }

        if (typeof yp === 'undefined') {
            y = $(container).scrollTop();
        } else {
            y = yp;
        }

        current_page = Parallax.getPage();

        y_norm = y / max_scroll;

        y_norm_to_current = (y - bounds[current_page - 1]) / (bounds[current_page] - bounds[current_page - 1]);

        runCallbacks();
    };

    return {
        init: function (config) {

            // no callbacks => no parallax
            if (callbacks.length === 0) {
                return;
            }

            setup(config);

            update();

            if (config.hasOwnProperty('setupCallback')) {
                config.setupCallback();
            } else {
                $(container)
                    .scroll(function (e) {
                        update();
                    });
            }

            $(window)
                .resize(function () {
                    clearTimeout(resizeTimeout);
                    resizeTimeout = setTimeout(function () {
                        setup(config);
                    }, 300);
                });
        },

        update: function (y) {
            update(y);
        },

        isPage: function (query) {
            if (y >= bounds[query - 1] && y < bounds[query]) {
                return true;
            }
            return false;
        },

        getPage: function () {
            var j;
            for (var j = 1; j <= bounds.length; j++) {
                if (Parallax.isPage(j)) {
                    return j;
                }
            }
        },

        addCallback: function (callback) {
            callbacks.push(callback);
        },

        disable: function () {
            disabled = true;
        },

        enable: function () {
            disabled = false;
        }
    }
}());