html图片懒加载，原理+demo

// 判断页面是否到了需要显示图片的位置并赋值
function loadlazy(){
    var itv = setTimeout(function(){
        var winHeight = $(window).height();
        var scrolltop = $(window).scrollTop();
        $(‘img‘).each(function(){
            var oTop = $(this).offset().top;
            if((oTop-scrolltop) >= 0 && (oTop-scrolltop)<winHeight){
                var src = $(this).attr("data_src");
                $(this).attr("src",src);
            }
        })
    },100);
}

// 页面滚动加载
$(window).scroll(function() {
    loadlazy();
});