해당 위치에 오면 숫자가 올락라는 스크립트

var isVisible = false;

$(window).on("scroll", function () {
  if (checkVisible($(".up_number")) && !isVisible) {
      var memberCountConTxt= 15;
  
  $({ val : 0 }).animate({ val : memberCountConTxt }, {
   duration: 2000,
  step: function() {
    var num = numberWithCommas(Math.floor(this.val));
    $(".memberCountCon").text(num);
  },
  complete: function() {
    var num = numberWithCommas(Math.floor(this.val));
    $(".memberCountCon").text(num);
  }
});

function numberWithCommas(x) {
    return x.toString().replace(/\B(?=(\d{3})+(?!\d))/g, ",");
}
    isVisible = true;
  }
});

function checkVisible( elm, eval ) {
    eval = eval || "object visible";
    var viewportHeight = $(window).height(), // Viewport Height
        scrolltop = $(window).scrollTop(), // Scroll Top
        y = $(elm).offset().top,
        elementHeight = $(elm).height();   
    
    if (eval == "object visible") return ((y < (viewportHeight + scrolltop)) && (y > (scrolltop - elementHeight)));
    if (eval == "above") return ((y < (viewportHeight + scrolltop)));
}

1개 사용중인데 4개로 늘리려고 합니다.

코드를 좀 짧게 짤 수 있을까요?