数值显示问题。。

if(typeof(Number.prototype.toFixed)!="function")
{
    Number.prototype.toFixed = function(d)
    {
        var s=this+"";if(!d)d=0;
        if(s.indexOf(".")==-1)s+=".";s+=new Array(d+1).join("0");
        if (new RegExp("^(-|\\+)?(\\d+(\\.\\d{0,"+ (d+1) +"})?)\\d*$").test(s))
        {
            var s="0"+ RegExp.$2, pm=RegExp.$1, a=RegExp.$3.length, b=true;
            if (a==d+2){a=s.match(/\d/g); if (parseInt(a[a.length-1])>4)
            {
                for(var i=a.length-2; i>=0; i--) {a[i] = parseInt(a[i])+1;
                if(a[i]==10){a[i]=0; b=i!=1;} else break;}
            }
            s=a.join("").replace(new RegExp("(\\d+)(\\d{"+d+"})\\d$"),"$1.$2");
        }if(b)s=s.substr(1);return (pm+s).replace(/\.$/, "");} return this+"";
    };
}var a = 9.920000000000008;
alert(a.toFixed(2));