JavaScript格式化数字的函数代码

/** 
* 格式化数字 
* Author : Z,Mingyu 
* 参数： 
* prmNum (Number) : 要格式化的数字 
* prmPtn (String) : 格式化规则，例如：#,##0.00 
* * prmNullValue : 当要格式化的数字为null、空或非数字时，返回的结果。默认为0 
*/ 
function formatNum(prmNum,prmPtn,prmNullValue){ 
var nullValue = prmNullValue ? prmNullValue : 0; 
if(prmNum == "" || prmNum == null) return nullValue; 
prmNum = prmNum.replace(/\,/g,""); 
if(isNaN(prmNum)) return nullValue; 
if(prmPtn == "" || prmPtn == null) return prmNum; 
var ptnLen = prmPtn.length; 
var pointIndex = prmPtn.indexOf("."); 
var groupIndex = prmPtn.indexOf(","); 
var pointLen = (pointIndex == -1 ? 0 : ptnLen - pointIndex - 1); 
prmNum = parseFloat(prmNum).toFixed(pointLen) + ""; 
if(groupIndex != -1){ 
if(pointIndex == -1) pointIndex = ptnLen; 
var len = pointIndex - groupIndex - 1; 
var reg = new RegExp("(-?\\d+)(\\d{"+len+"})"); 
while(reg.test(prmNum)) prmNum = prmNum.replace(reg,"$1,$2"); 
} 
return prmNum; 
}