格式化美元 javascript

function formatDollar(num,floatNum,zeroASNA){

     if(floatNum == null){

         floatNum = 2;

     }

     if(num == null || num <= 0){

         if(zeroASNA || zeroASNA == null && num <=0){

             return "N/A";

         }else if(num == null){

             return "N/A";

         }

     }

     var string = num.toFixed(floatNum);

     var parts = string.split('.');

     var cents = 0;

     if(parts.length > 1){

         cents = parts.pop();

     }

     var dollars = parts.shift();

     dollars = dollars.replace(/(/d{1,2}?)((/d{3})+)$/, "$1,$2");

     dollars = dollars.replace(/(/d{3})(?=/d)/g, "$1,");

     if(cents > 0){

         return '$' + dollars + '.' + cents;

     }else{

         return '$' + dollars;

     }

}