How to change JS's alert style like background color

Copy code code as follows:

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";

// The background color when the dialog box pops up

shield.style.background = "#fff";

shield.style.textalign = "Center";

shield.style.zindex = "25";

// Background transparent IE is valid

//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 = "<ul style =/" list-style: none; margin: 0px; padding: 0px; width: 100%/">/n";

strhtml += "<li style =/" background:#dd828d; text-alft; padding-left: 20px; font-size: 14px; font-weight: bold; height: 25px; l INE-Height: 25px; border : 1px solid #f9cade;/"> [custom prompt] </li>/n";

Strhtml += "<li style =/" background: #fff; text-align: center; font-size: 12px; height: 120px; line-height: 120px; 1px solid Ade; Border-Right: 1px solid #f9cade;/">"+str+"</li>/n";

Strhtml += "<li style =/" background: #fdeef4; text-align: center; font-weight: bold; height: 25px; line-height: 25px; 1px solid #F 9Cade;/"> <input Type =/"Button/" Value =/"OK/" OnClick =/"DOOK ()/"/> </li>/N ";

strhtml += "</ul>/n";

alertfram.innerhtml = strhtml;

document.body.appendchild (alertfram);

document.body.appendchild (shield);

var adj = SetInterval ("DOALPHA ()", 5); 5);

this.Dook = Function () {

alertfram.style.display = "None";

shield. Style.display = "None";

}

alertfram.focus ();

document.body.OnselectStart = Function () {Return false;};

}

The effect is as shown in the figure