js的alert样式如何更改如背景颜色_javascript技巧

window.alert = function(str)

{

var shield = document.createElement("DIV");

shield.id = "shield";

shield.style.position = "absolute";

shield.style.left = "0px";

shield.style.top = "0px";

shield.style.width = "100%";

shield.style.height = document.body.scrollHeight+"px";

//弹出对话框时的背景颜色

shield.style.background = "#fff";

shield.style.textAlign = "center";

shield.style.zIndex = "25";

//背景透明 IE有效

//shield.style.filter = "alpha(opacity=0)";

var alertFram = document.createElement("DIV");

alertFram.id="alertFram";

alertFram.style.position = "absolute";

alertFram.style.left = "50%";

alertFram.style.top = "50%";

alertFram.style.marginLeft = "-225px";

alertFram.style.marginTop = "-75px";

alertFram.style.width = "450px";

alertFram.style.height = "150px";

alertFram.style.background = "#ff0000";

alertFram.style.textAlign = "center";

alertFram.style.lineHeight = "150px";

alertFram.style.zIndex = "300";

strHtml = "

\n";

strHtml += "
• [自定义提示]

\n";

strHtml += "

• "+str+"

\n";

strHtml += "

\n";

strHtml += "

\n";

alertFram.innerHTML = strHtml;

document.body.appendChild(alertFram);

document.body.appendChild(shield);

var ad = setInterval("doAlpha()",5);

this.doOk = function(){

alertFram.style.display = "none";

shield.style.display = "none";

}

alertFram.focus();

document.body.onselectstart = function(){return false;};

}