How to do hard things(drmaciver.com)

  function RecFunc(n, max) {
    let result; // intialize the return variable
    if (n < max) {
      result = RecFunc(n + 1, max) // the recursion
    } else {
      result = n; // the exit condition
    }
    return result;
  }
  RecFunc(0, 3);

  | RecFunc
  v   n: 0, max: 3, result: undefined
  |   RecFunc
  v     n: 1, max: 3, result: undefined
  |     RecFunc
  v       n: 2, max: 3, result: undefined
  |       RecFunc
  v         n: 3, max: 3, result: 3

  ^ RecFunc
  |   n: 0, max: 3, result: 3
  ^   RecFunc
  |     n: 1, max: 3, result: 3
  ^     RecFunc
  |       n: 2, max: 3, result: 3
  ^       RecFunc
  |         n: 3, max: 3, result: 3

  var result = 0;
  for (var i=0; i++; i<=3) {
    result += 1;
  }

  # imagine we're recursing to subtract to zero

  1. call function subtract with 10 (set x = 10)
  2. subtract x by 1
  3. if zero, return 0
  4. else return the result of calling the function with x-1 (jump to 2)

  - A leaf, which is the end (has no children)
  - A branch, which may have leaves or more branches (has children)... and because a branch can have more branches, this is recursion, so we abstract to a 3rd type of part:
  - A node, which could be a branch or a leaf...

  function int getNumLeaves(Node node):
    foreach childNode in node:
      if childNode.IsLeaf(): leafCount++
      else: return getNumLeaves(childNode) // NOT a leaf -> check this branch's children

  print getNumLeaves(tree.stem); // (start with the outermost 'node')

  function myFunc(list) {
    // exit condition
    if (list.length == 0) {
      // What should the function do if the exit condition is true
      return
    } else {
      // before recursion
      console.log(list[0])
      
      // recursion
      myFunc(list.slice(1))
      
      // after recursion
    }
  }