原生Js页面滚动延迟加载图片实现原理及过程_javascript技巧

//添加图片list
var _temp = [];
for (var i = 1; i < 21; i ++) {
_temp.push('
图片' + i);
}
_CalF.$("#content").innerHTML = _temp.join("");

function scrollLoad(){
this.init.apply(this, arguments);
}
scrollLoad.prototype ={
init : function(className){
var className = "img."+className,
imgs = _CalF.$(className),
that = this;
this.imgs = imgs;
that.loadImg();
window.onscroll = function(){
that.time = setTimeout(function(){
that.loadImg();
},400);
}
},
loadImg : function(){
var imgs = this.imgs.reverse(), //获取数组翻转
len = imgs.length;
if(imgs.length===0){
clearTimeout(this.time);
return;
}
for(var j=len-1;j>=0;j--){ //递减
var img = imgs[j],
imgTop = _CalF.getPosition(img).top,
imgSrc = img.getAttribute("data-src"),
offsetPage = window.pageYOffset ? window.pageYOffset : window.document.documentElement.scrollTop,//滚动条的top值
bodyHeight = document.documentElement.clientHeight; //body的高度
if((offsetPage+bodyHeight/2) > (imgTop-bodyHeight/2)){
img.src = imgSrc;
this.imgs.splice(j,1);
}
}
}
}

var img1 = new scrollLoad("scrollLoading");