Trie.js - super simple JavaScript implementation

Trie.js

// Trie.js - JS implementation
// https://en.wikipedia.org/wiki/Trie

// Inspired by Tpae's implementation

// we start with the TrieNode
function TrieNode(key) {
  // the "key" value will be the character in sequence
  this.key = key;

  // we keep a reference to parent
  this.parent = null;

  // we have hash of children
  this.children = {};

  // check to see if the node is at the end
  this.end = false;
}

// iterates through the parents to get the word.
// time complexity: O(k), k = word length
TrieNode.prototype.getWord = function() {
  var output = [];
  var node = this;

  while (node !== null) {
    output.unshift(node.key);
    node = node.parent;
  }

  return output.join('');
};

// -----------------------------------------

// we implement Trie with just a simple root with null value.
function Trie() {
  this.root = new TrieNode(null);
}

// inserts a word into the trie.
// time complexity: O(k), k = word length
Trie.prototype.insert = function(word) {
  var node = this.root; // we start at the root 😬

  // for every character in the word
  for(var i = 0; i < word.length; i++) {
    // check to see if character node exists in children.
    if (!node.children[word[i]]) {
      // if it doesn't exist, we then create it.
      node.children[word[i]] = new TrieNode(word[i]);

      // we also assign the parent to the child node.
      node.children[word[i]].parent = node;
    }

    // proceed to the next depth in the trie.
    node = node.children[word[i]];

    // finally, we check to see if it's the last word.
    if (i == word.length-1) {
      // if it is, we set the end flag to true.
      node.end = true;
    }
  }
};

// returns every word with given prefix
// time complexity: O(p + n), p = prefix length, n = number of child paths
Trie.prototype.find = function(prefix) {
  var node = this.root;
  var output = [];

  // for every character in the prefix
  for(var i = 0; i < prefix.length; i++) {
    // make sure prefix actually has words
    if (node.children[prefix[i]]) {
      node = node.children[prefix[i]];
    } else {
      // there's none. just return it.
      return output;
    }
  }

  // recursively find all words in the node
  findAllWords(node, output);

  return output;
};

export default Trie