ajax请求完之前的loading加载

 1 /*loading.js*/
 2 // 加载HTML图
 3 var _LoadingHtml = '<div id="loadingDiv" style="position:fixed;left: 0;top: 0;right: 0;bottom: 0;z-index: 99999;background-color: #fff;"><div style="position: fixed;top: 50%;left: 50%;transform: translate(-50%,-50%);"><img src="images/loading.gif" style="vertical-align: middle;width: 100px;">加载中。。。</div></div>';
 4 
 5 // 呈现loading效果
 6 document.write(_LoadingHtml);
 7 
 8 // 监听加载状态改变
 9 document.onreadystatechange = completeLoading;
10 
11 // 加载状态为complete时移除loading效果
12 function completeLoading() {
13     if (document.readyState == "complete") {
14         var loadingMask = document.getElementById('loadingDiv');
15         loadingMask.parentNode.removeChild(loadingMask);
16     }
17 }