<p id="result"></p>
function insertNum(num1,num2,sumCallback){
  return sumCallback(num1,num2);
}

function sumCallback(num1,num2){
  return num1 + num2;
}

var result = insertNum(1,1,sumCallback);

document.getElementById('result').innerHTML = result;

External CSS

This Pen doesn't use any external CSS resources.

External JavaScript

This Pen doesn't use any external JavaScript resources.