/*
**格式化数值函数
**四舍六入，逢五则奇进偶不进
*/
Number.prototype.toFixedA=function(len)
{
    var add = 0;
    var s;
    var temp = Math.pow(10,len+1);
    s = Math.floor(this * temp);
    var s1 = this + "";
    var start = s1.indexOf(".");
    var num1=s1.substr(0,start);
    var num2="0"+s1.substr(start);
var s2=s1.substr(start+len,1);
    if(s1.substr(start+len+1,1)>5){
 
     add=1;
    }else {
     if(s1.substr(start+len+1,1)==5){
      if(num2==(s/temp).sub1()){
       if(chk(s2)==1) add=1;
      }else{
 add=1;
}
     }
    }
    var temp1 = Math.pow(10,len);
    var s3 = Math.floor(this * temp1) + add;
    return (s3/temp1).toFixed(len);
}
/*
**格式化数值函数
**将浮点数精确到 0.5（即只能出现 12.0 12.5 不能出现 12.2 12.6 )
*/
function toFormatA(f)
{
    var fTemp = f * 10 ;
    var sTemp = "" + fTemp ;
    
    var i = parseInt(sTemp.substr(sTemp.length - 1 , 1) );
    
    if(i == 0 ){
        return f + ".0" ;
    }else if(i == 5){
        return f ;
    }else if(i < 5 && i != 5){
        sTemp = sTemp.substr(0 , sTemp.length - 1) + "0";
        return parseFloat(sTemp / 10) + ".0" ;
    }else if(i > 5 && i != 5){
        return parseInt( parseFloat(f) + 1 ) + ".0" ;
    }else{
        return "数值错误,请检查!";
    }
}