JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.0.0-beta1/jquery.min.js"></script>
<button id="button">
  Increment A
</button>
<div id="id">

</div>
<script>
  function outer() {
    var a;
    var b;
    var $selector;

    var retObj = {
      init: function() {
        a = 10;
        b = 5;
        $selector = $("#id");
        attachEventHandlers();
      }
    };

    function attachEventHandlers() {
      $("#button").click(function() {
        //place a debug point here and then in the console
        //b would not be defined
        //change the below statement to a = a+b, and in the console
        //b would be defined with the correct value
        a = a + 1;
        $selector.html(a);
      });
    }

    return retObj;
  }
  var obj = outer();
  obj.init();

</script>