JSFiddle - React, Tailwind, and code Playground

JavaScript

// Using IIFE, to not to pollute global namespace.
(function(){

  var addFn = function addFn(){

    var total = 0;
    return function(val){
      total += val;
      return total;
    }

  };

  var add = addFn();

  console.log(add(5));
  console.log(add(20));
  console.log(add(3));
  
}());