SYMBOL INDEX (5 symbols across 4 files)

FILE: code/1.js
  function addOne (line 5) | function addOne() { myNumber++ } // define the function

FILE: code/2.js
  function addOne (line 7) | function addOne() {

FILE: code/3.js
  function addOne (line 7) | function addOne(callback) {
  function logMyNumber (line 15) | function logMyNumber() {

FILE: code/4.js
  function takesOneSecond (line 1) | function takesOneSecond(callback) {