关于两个setInterval 替换<img>.url和<div>.background的问题

Question

关于两个setInterval 替换<img>.url和<div>.background的问题

<div id="loading_bg" style="background:url("img/loading/loading_bg0.png") no-repeat;background-size: cover;">
    <img src="img/loading/loading_icon0.png" alt="" id="loading_icon">
</div>

<----------------->

var bgCount = 0;var iconCount = 0;
setInterval(changbg,100);
function changbg() {
    document.getElementById('loading_bg').setAttribute('style','background:url("img/loading/loading_bg'+bgCount%7+'.png") no-repeat;background-size:cover;');
    bgCount++;
}
setInterval(changeicon,100);
function changeicon() {
    document.getElementById('loading_icon').setAttribute('src','img/loading/loading_icon'+iconCount%3+'.png');
    iconCount++;
}

问题是

img.src的图片一致持续在循环请求，然而外层的div.background.url并没再请求。
请问这是什么原因？以及如何解决循环加载的问题？
扣谢~

Answer 1

id 写错了，document.getElementById('loading_bg') => document.getElementById('loadingStar')