基于JavaScript实现图片点击弹出窗口而不是保存

<script>
function picHook(pic){
/*图片对象*/
var imgs = document.getElementsByTagName("img");
/*前景div*/
var light = document.getElementById('light') || document.createElement("div");
/*背景div*/
var bg = document.getElementById('bg') || document.createElement("div");
/*图片放大*/
var s_pic = document.getElementById('s_pic') || document.createElement("img");
/*css对象*/
var css = document.createElement("style");
/*css样式*/
var csstext = '\
.pic_bg{\
position: absolute;\
margin:0 auto; \
top: 0%;\
left: 0%;\
width: 100%;\
padding-bottom: 1000%;\
background-color: black;\
z-index:1001;\
opacity:.80;\
filter: alpha(opacity=80);\
overflow:scroll;\
}\
.pic_div {\
margin-bottom: auto;\
position: fixed;\
left:50%;\
top:50%;\
margin-left:-250px;\
margin-top:-100px;\
z-index:1002;\
}';
/*收集页面所有图片对象*/
for(i=0; i<imgs.length;i++){
imgs[i].setAttribute("onclick", "picHook(this)" );
}
css.type = "text/css";

/*关闭图像*/
if( !pic ){
bg.style.display = light.style.display = "none";
}
/*ie兼容*/
if(css.styleSheet){
css.styleSheet.cssText = csstext;
}else{
css.appendChild(document.createTextNode(csstext));
}
s_pic.setAttribute("id", "s_pic");
s_pic.setAttribute("src", pic.src);
light.setAttribute("id", "light");
light.setAttribute("class", "pic_div");
light.style.display = 'block';
light.appendChild(s_pic);
bg.setAttribute("id", "bg");
bg.setAttribute("class", "pic_bg");
bg.setAttribute("onclick", "picHook()");
bg.style.display = light.style.display;
document.getElementsByTagName("head")[0].appendChild(css); 
document.body.appendChild(bg);
document.body.appendChild(light);
}
</script>