jQuery.imgLazyLoad图片懒加载组件

/**
 * component: imgLazyLoad 2013/12/12 华子yjh
 * invoking: jQuery.imgLazyLoad(options)
 *
    // 配置对象
    options = {
        container: ‘body‘,              // 外围容器，默认body
        tabItemSelector: ‘‘,            // Tab切换面板选择器
        carouselItemSelector: ‘‘,       // 图片轮播面板选择器
        attrName: ‘imglazyload-src‘     // 图片地址属性
        diff: 300                       // 预加载像素
    }
 *
 */

$.extend({
    imgLazyLoad: function(options) {
        var config = {
                container: ‘body‘,
                tabItemSelector: ‘‘,
                carouselItemSelector: ‘‘,
                attrName: ‘imglazyload-src‘,
                diff: 0
            };
        $.extend( config, options || {} );

        var $container = $(config.container),
            offsetObj = $container.offset(),
            compareH = $(window).height() + $(window).scrollTop(),

            // 判断容器是否为body子元素
            bl = $.contains( document.body, $container.get(0) ),

            // 过滤缓存容器中的图片
            notImgSelector = jQuery.imgLazyLoad.selectorCache ? ‘:not(‘ + jQuery.imgLazyLoad.selectorCache + ‘)‘ : ‘‘,
            imgSelector = ‘img[‘ + config.attrName + ‘]:visible‘ + notImgSelector,
            $filterImgs = $container.find(imgSelector),

            // 用于阻止事件处理
            isStopEventHandle = false,
            
            // 是否自动懒加载，为true时，绑定滚动事件
            isAutoLazyload = false;

        // 缓存容器为body子元素的图片选择器
        jQuery.imgLazyLoad.selectorCache = bl ? (jQuery.imgLazyLoad.selectorCache ? (jQuery.imgLazyLoad.selectorCache + ‘,‘ + config.container + ‘ img‘) : config.container + ‘ img‘) : jQuery.imgLazyLoad.selectorCache;

        function handleImgLoad(idx) {
            if (isStopEventHandle) {
                return;
            }
            /**
             处理Tab切换，图片轮播，在处理$filterImgs时，没有过滤img:not(.img-loaded)，因为只是在一个面板中，
             还有其他面板，如果再次触发，可能$filterImgs.length为0，因此只能在外围容器中判断过滤图片length
            */            
            if ($container.find(‘img:not(.img-loaded)‘).length === 0) {
                isStopEventHandle = true;
            }

            var itemSelector = config.tabItemSelector || config.carouselItemSelector || ‘‘;
            if (itemSelector) {
                if (typeof idx !== undefined && idx >= 0) {
                    $filterImgs = $container.find(itemSelector).eq(idx).find(‘img‘);
                }
                else {
                    if (itemSelector === config.carouselItemSelector) {
                        $filterImgs = $container.find(itemSelector).eq(0).find(‘img‘);
                    }
                    else {
                        $filterImgs = $container.find(itemSelector + ‘:visible‘).find(‘img‘);
                    }
                }
            }
            else {
                $filterImgs = $filterImgs.not(‘.img-loaded‘); // 自动懒加载，过滤已加载的图片
                isAutoLazyload = true;
            }

            // 当外围容器位置发生变化，需更新
            offsetObj = $container.offset();

            if ($filterImgs.length > 0) {
                $filterImgs.each(function(idx, elem) {
                    var $target = $(elem),
                        targetTop = $target.offset().top,
                        viewH = $(window).height() + $(window).scrollTop() + config.diff;

                    if (bl) {
                        $target.attr(‘src‘, $target.attr(config.attrName)).removeAttr(config.attrName).addClass(‘img-loaded‘);
                    }
                    // 内容在视窗中
                    if (viewH > targetTop) {
                        $target.attr(‘src‘, $target.attr(config.attrName)).removeAttr(config.attrName).addClass(‘img-loaded‘);
                    }
                });
            }
            else {
                // 处理滚动事件
                isStopEventHandle = true;
                $(window).unbind(‘resize scroll‘, handleImgLoad);
            }
        }

        handleImgLoad();
        if (isAutoLazyload) {
            $(window).bind(‘resize scroll‘, handleImgLoad);
        }

        // 提供事件处理函数
        return {
            handleImgLoad: handleImgLoad
        }
    }
});

// 保存非body子元素容器下的图片选择器
jQuery.imgLazyLoad.selectorCache = ‘‘;

// 轮播图片 懒加载
(function(){
    var imgLazyLoadObj = $.imgLazyLoad({
        container: ‘#first-block-switch‘,
        carouselItemSelector: ‘.switch-content li‘
    });
    $.switchable({
        wrapSelector: ‘#first-block-switch‘,
        contentSelector: ‘.switch-content‘,
        prevBtnSelector: ‘.prev‘,
        nextBtnSelector: ‘.next‘,
        triggerSelector: ‘.switch-nav‘,
        autoPlay: true,
        duration: 300,
        interval: 3000,
        handleImgLoad: imgLazyLoadObj.handleImgLoad
    });
}());

// 浏览器滚动 懒加载
$.imgLazyLoad({ diff: 300 });