在js中如何打印菱形

document.write(" <center> ");var row=Number(prompt("输入行数"));for(var i=1;i<=2*row-1;i++){    var stars=2*row-1-2*Math.abs(i-row);//星    for(var j=1;j<=stars;j++){        document.write(" * ");    }    document.write("<br>");}