금액 입력시 자동으로 천단위구분기호(,) 붙여주는 함수

function checkNumber(decimals,dec_point,thousands_sep){
var objEv = event.srcElement;
var numPattern = /([^0-9,-,\,])/;
numPattern = objEv.value.match(numPattern);
if(numPattern != null){
alert("숫자로 입력해주십시오.");
objEv.value="";
objEv.focus();
return false;
}

if(objEv.value.indexOf('-') > 1){
alert("숫자로 입력해주십시오.");
objEv.value="";
objEv.focus();
return false;
}

if(decimals==null){decimals=999;}
if(dec_point==null){dec_point='.';}
if(thousands_sep==null){thousands_sep=',';}

var arr = objEv.value.toString().replace(/[^-\.\+\d]/g,'').split(dec_point);

arr[0] = arr[0].replace(/(\d)(?=(?:\d{3})+(?!\d))/g,'$1'+thousands_sep);

if(arr[1] && decimals>0 && arr[1].length>0){
objEv.value= arr[0] + dec_point + arr[1];
return true;

} else{
objEv.value= arr[0];
return true;

}

}