made by C.L

function alterfmt(obj) {
    var val = obj.value.replace(/,/g,'');
    var tp=new Array(val.length);
    var chars = ",0123456789";

    if ( obj.value.length > 1 ) {
        for (var x=0; x < val.length; x++) {
            if (chars.indexOf(val.charAt(x)) == -1) {
                alert('숫자만 입력가능합니다');
                return false;
            }
            tp[x] = val.charAt(x);
        }
        tp=tp.reverse();
        for ( var i=(tp.length-1); i>0; i-- ) {
            if ( i > 0 && !(i%3) ) {
                tp[i]=tp[i]+",";
            }
        }
        tp=tp.reverse();
        obj.value = tp.join("");
        return true;
    }
}