javascript四舍五入 保留后几位的函数代码

/**
* 四舍五入 保留后几位
* by www.jquerycn.cn
*/
function FormatNumber(srcStr,nAfterDot){
  var srcStr,nAfterDot;
  var resultStr,nTen;
  srcStr = ""+srcStr+"";
  strLen = srcStr.length;
  dotPos = srcStr.indexOf(".",0);
  if (dotPos == -1){
    resultStr = srcStr+".";
    for (i=0;i<nAfterDot;i++){
      resultStr = resultStr+"0";
    }
  }
  else{
    if ((strLen - dotPos - 1) >= nAfterDot){
      nAfter = dotPos + nAfterDot + 1;
      nTen =1;
      for(j=0;j<nAfterDot;j++){
        nTen = nTen*10;
      }
      resultStr = Math.round(parseFloat(srcStr)*nTen)/nTen;
    }
    else{
      resultStr = srcStr;
      for (i=0;i<(nAfterDot - strLen + dotPos + 1);i++){
        resultStr = resultStr+"0";
      }
    }
  }
 return resultStr;
}