JSFiddle - React, Tailwind, and code Playground

HTML

<div id="choice"></div>

<div id="hidden">

</div>

CSS

#hidden {display:none}

JavaScript

var Calculator = {
  average: function(x) {
    var num = 0;
      for (var i = 0; i < x.length; i++){
        num = num + x[i];      
      }
    var divide = num/x.length;
    return divide;
 }
};

document.getElementById('choice').innerHTML = Calculator.average([3,4,5]);