JS Data structures - trie

trie.js

function Trie() {
  this.children = {}
  this.value = null
}

Trie.prototype.isLeaf = function() {
  return Object.keys(this.children).length === 0
}

Trie.prototype.isFree = function() {
  return !this.value
}

Trie.prototype.find = function(item) {
  var node = this
  for (var idx in item) {
    var char = item[idx]
    if (node.children[char]) {
      node = node.children[char]
    } else {
      return null
    }
  }
  
  return node.value
}

Trie.prototype.insert = function(item) {
  var node = this
  for (var idx in item) {
    let char = item[idx]
    if (node.children[char]) {
      node = node.children[char]
    } else {
      break;
    }
  }
  
  while(idx < item.length) {
    var char = item[idx]
    node.children[char] = new Trie()
    node = node.children[char]
    idx++
  }
  
  node.value = item
}

Trie.prototype.delete = function(item) {
  function deleteRec(node, level) {
    if (level === item.length) {
      delete node.value
      return node.isFree()
    } else {
      var char = item[level]
      if (deleteRec(node.children[char], level + 1)) {
        delete node.children[char]
        return node.isFree() && node.isLeaf()
      }
    }
  }
  
  deleteRec(this, 0)
}