How to implement a Trie in JavaScript

function Trie(letter = '') {
  this.value = letter;
  this.children = {};
  this.isWord = false;
}
Trie.prototype.add = function(word, node = this) {
  
  for (const letter of word) {
    if (node.children[letter]) {
      node = node.children[letter];
    } else {
      const newNode = new Trie(letter);
      node.children[letter] = newNode;
      node = newNode;
    }
  }
  
  node.isWord = true;
};
Trie.prototype.find = function(word, node = this) {
  let value = ''
  
  for (const letter of word) {
    if (node.children[letter]) {
      node = node.children[letter];
      value += letter;
    }
  }
  return value === word ? node : null;
};
Trie.prototype.remove = function(word = '', node = this) {
  if (!word) return null;
  
  const chain = [];
  
  // traverse down trie
  for (const letter of word) {
    if (node.children[letter]) {
      chain.push(node) // we want all nodes accessible in chain so we can move backwards and remove dangling nodes
      node = node.children[letter]
    } else {
      return null; // word is not in trie
    }
  }
  
  if (Object.keys(node.children).length) { // if any children, we should only change isWord flag
    node.isWord = false;
    return node;
  }
  
  // Zero children in node.
  // continue until we hit a breaking condition
  let child = chain.length ? chain.pop() : null; // whatever node was
  let parent = chain.length ? chain.pop() : null; // if node has parent
  while (true) {
    child && parent && delete parent.children[child.value]; // remove child;
    
    if (Object.keys(parent.children).length || !chain.length) { // if more children or chain is empty, we're done!
      node.isWord = false;
      return node;
    }
    // otherwise, we have no more children for our parent and we should keep deleting nodes
    // our next parent is what we pop from the chain
    // our child is what our parent was.
    child = parent;
    parent = chain.pop()
  }
};
Trie.prototype.findWords = function(value = '', node = this.find(value), words = []) {
  Object.values(node.children).forEach((child) => {
    if (child.isWord) words.push(value + child.value);
    child.findWords(value + child.value, child, words);
  });
  
  return words;
};
Trie.prototype.hasWord = function(word) {
  const node = this.find(word);
  return !!node && node.isWord; 
};