js 弹出框 替代浏览器的弹出框

function fromID(id) { 
return document.getElementById(id); 
} function show_alert(msg, type, time) { 
var layer_obj = fromID("alert_layer"); 
var layer_text= fromID("alert_text"); 
var line_height = (document.documentElement.scrollTop == 0) ? document.body.scrollTop : document.documentElement.scrollTop; 
layer_text.innerHTML = msg; 
with(layer_obj.style) { 
zIndex = 999; 
top = line_height-40; 
left = document.body.clientWidth/3; 
display = "block"; 
position = "absolute"; 
if(type == "error") { 
background = "url(http://"+style_domain+"/snake/index/msgbox_right_bg2.jpg)"; 
} 
} 
layer_obj.filters[0].opacity = "0.8"; //透明度为 80% 
if(time == undefined) time = 3000; 
else time = time*1000; 
var top = line_height-40; 
var speed = 1.5; 
time-= 1000; 
//控制窗口向下移动至页面边缘 
move_down = function MoveFplogo() { 
top+= speed; 
layer_obj.style.top = top; 
if(top < line_height) setTimeout("move_down()", 1); 
else setTimeout("close_alert_win()", time); 
} 
move_down(); 
} 
function close_alert_win() { 
var layer_obj = fromID("alert_layer"); 
//控制窗口渐渐消失 
if(layer_obj.filters[0].opacity < 0.02) { 
layer_obj.style.display = "none"; 
return true; 
} 
layer_obj.filters[0].opacity-= 0.02; 
setTimeout("close_alert_win()", 1); 
} 
document.writeln(" filter:progid:DXImageTransform.Microsoft.BasicImage();">"); 
document.writeln(" "); 
document.writeln(" "); 
document.writeln("");