var loadHeight=61;

var loadWidth=215;

//获取浏览器页面可见高度和宽度

var _PageHeight = document.documentElement.clientHeight,

    _PageWidth = document.documentElement.clientWidth;

//计算loading框距离顶部和左部的距离（loading框的宽度为215px，高度为61px）

var _LoadingTop = _PageHeight > loadHeight ? (_PageHeight - loadHeight) / 2 : 0,

    _LoadingLeft = _PageWidth > loadWidth ? (_PageWidth - loadWidth) / 2 : 0;

//在页面未加载完毕之前显示的loading Html自定义内容 默认背景:#f3f8ff

var _LoadingHtml = '<div id="loadingDiv" style="position:absolute;left:0;width:100%;height:' + _PageHeight + 'px;top:0;background:#fff;opacity:0;-moz-opacity:0;filter:alpha(opacity=0);z-index:10000;"><div style="position: absolute; cursor1: wait; left: ' + _LoadingLeft + 'px; top:' + _LoadingTop + 'px; width:100px;; height: 50px;display: inline-block; line-height: 50px; text-align:center; background: #fff  no-repeat scroll 5px 12px; border: 2px solid #95B8E7; color: #696969; font-family:\'Microsoft YaHei\';">加载中...</div></div>';

//呈现loading效果

document.write(_LoadingHtml);

//监听加载状态改变

document.onreadystatechange = completeLoading;

//加载状态为complete时移除loading效果

function completeLoading() {

    if (document.readyState == "complete") {

        var loadingMask = document.getElementById('loadingDiv');

        loadingMask.parentNode.removeChild(loadingMask);

    }

}