1.html代码：

2.js代码：

imgobj=document.getElementById('imgid');//可视区域的高（视口高-图片所占的高度）screenHeight=document.documentElement.clientHeight;imgHeight=158;/*imgobj.clientHeight*/diffHeight=screenHeight-imgHeight;

//可视区域的宽（视口宽-图片所占的宽度）

screenWidth=document.documentElement.clientWidth;

imgWidth=162;/*imgobj.clientWidth*/

diffWidth=screenWidth-imgWidth;

ys=0;

yv=100;

xs=0;

xv=100;

setInterval(function(){

//y轴坐标

ys+=yv;

if (ys>=diffHeight) {

ys=diffHeight;

yv=-yv;

}

if (ys<=0) {

yv=-yv;

}

imgobj.style.top=ys+'px';

//x轴坐标

xs+=xv;

if (xs>=diffWidth) {

xs=diffWidth;

xv=-xv;

}

if (xs<=0) {

xv=-xv;

}

imgobj.style.left=xs+'px';

},100);