Contacts Problem in ES6, people still know what Rolodexs are right?

Rolodex.js

#!/usr/bin/env node
"use strict"

// hackerrank https://www.hackerrank.com/challenges/ctci-contacts/problem
// add hack
// add hackerrank
// find hac
// find hak
// var alphabet = 'abcdefghijklmnopqrstuvwxyz'
class Rolodex {
  constructor(debug) {
    this.masterNode = new Node()
    this.debug = debug
  }

  add(str) {
    if (this.debug) console.log("starting add: ", str)
    var strArr = str.split('')
    var node = new Node(strArr.shift())
    node = this.masterNode.addChild(node, (strArr.length == 1), this.debug)
    while(strArr.length > 0) {
      if (this.debug) console.log("while loop adding: ", strArr[0])
      var newNode = new Node(strArr.shift(), (strArr.length == 1), this.debug)
      node = node.addChild(newNode)
    }
    if (this.debug) {
      console.log("masterNode: ")
      console.dir(this.masterNode)
    }
  }

  find(str) {
    var count = 0
    if (this.debug) console.log("finding: ", str)
    var strArr = str.split('')
    var node = this.masterNode
    while(node && strArr[0]) {
      if (this.debug) console.log("getting child: ", strArr[0])
      var child = node.getChildNode(strArr.shift())
      if (child && strArr.length == 0) {
        if (this.debug) console.log("child count: ", node.count)
        count = child.count
      }
      node = child
    }
    console.log(count)
    return count
  }
}

class Node {
  constructor(letter, last, debug) {
    this.children = []
    this.letter = letter
    this.isLast = last
    this.count = 1
    this.debug = debug
  }

  getCharCode(letter) {
    return letter.charCodeAt(0) - 97
  }

  getChildNode(letter) {
    if (!letter) return
    return this.children[this.getCharCode(letter)]
  }

  setChildNode(node) {
    this.children[this.getCharCode(node.letter)] = node
  }

  addChild(node) {
    if (this.debug) {
      console.log("adding child: ", node.letter, "to: ", this.letter)
      console.log("current node: ", this.letter, "children: ", this.children)
    }
    var child = this.getChildNode(node.letter)
    if (child) {
      child.count += 1
      if (this.debug) console.log("child found:", child)
      return child
    } else {
      if (this.debug) console.log("child missing:", node.letter)
      this.setChildNode(node)
      return node
    }
  }
}

var r = new Rolodex()
r.add("hack")
r.add("hacker")
r.add("hackist")
r.add("beer")
r.add("bee")
r.add("beet")
r.add("bear")
r.add("beast")
r.add("feet")
r.add("foot")

r.find("hac")
r.find("hak")
r.find("bee")
r.find("bea")
r.find("f")
r.find("zebra")