百分比形式保留小数点后2位（且四色五入）

//有效位数
function math(num,v)
{
    var vv = Math.pow(10,v);
    return Math.round(num*vv)/vv;
}
//预算完成率
function percentage2(){
var thisIncomePlan=document.getElementById("thisIncomePlan").value;
var thisIncomeTotal=document.getElementById("thisIncomeTotal").value;
if(thisIncomePlan!=""&&thisIncomeTotal!=""&&isNaN(thisIncomePlan)==false&&isNaN(thisIncomeTotal)==false){
var dd=thisIncomeTotal/thisIncomePlan;
document.getElementById("budget").innerHTML=(Math.round((math(dd,6)*100)*100)/100).toFixed(2)+"%";
}
}