<button class="up325"></button>
<button class="down325"></button>
<input class="qntc325" value="0"/>
[class*="325"]:before {
  content: " ["attr(class) "] "
}
$(document).ready(function() {
 
  $('.up325').on('click',function(){
    var num1 = $(this).parent().find('.qntc325').val();
    var max1 =4;
    if(num1 < max1){
      $(this).parent().find('.qntc325').val(parseInt(num1)+1);
    }
  });

  $('.down325').on('click',function(){
    var num1 = $(this).parent().find('.qntc325').val()-1;

    if(num1 == 0) {
      num1 = 1;
    }
    $(this).parent().find('.qntc325').val(parseInt(num1));
  });
});

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

  1. https://cdnjs.cloudflare.com/ajax/libs/jquery/3.7.1/jquery.min.js