Javascript Trie for efficient prefix search

trie.js

class Node {
  constructor(char, parent = null, weight = null) {
    this.char = char;
    this.parent = parent;
    this.weight = weight;
    this.children = {};
  }
  
  get isTerminal() {
    return this.weight !== null;
  }
  
  toString() {
    if (this.isTerminal) {
      return `(${this.char}=${this.weight})`;
    }
    
    return `(${this.char} ${Object.values(this.children).map(child => child.toString()).join(' ')})`;
  }
}

function insert(node, word, weight) {
  if (!node || !word) {
    return;
  }
  
  const c = word.charAt(0);
  const nextWord = word.substring(1);
  
  let child = node.children[c];
  if (!child) {
    child = new Node(c, node);
    node.children[c] = child;
  }
  
  if (nextWord.length === 0) {
    child.weight = weight;
    return child;
  }

  return insert(child, nextWord, weight);
}

function find(node, word, prefix = '', results = []) {
  if (!node) {
    return results;
  }
  
  if (node.isTerminal) {
    return results.concat([
      { word: prefix + node.char, weight: node.weight }
    ]);
  }
  
  if(!word) {
    return Object.values(node.children).reduce(
      (prevResults, matchingNode) => find(matchingNode, '', prefix + node.char, prevResults),
      results
    );
  }
  
  const c = word.charAt(0);
  const nextWord = word.substring(1);
  const nextNode = node.children[c];
  
  if (!nextNode) {
    return results;
  }
  
  return find(nextNode, nextWord, prefix + node.char, results);
}

class Trie {
  constructor() {
    this.root = new Node('');
  }
  
  insert(word, weight) {
    return insert(this.root, word, weight);
  }
  
  find(word) {
    return find(this.root, word);
  }
        
  toString() {
    return this.root.toString();
  }
}

let t = new Trie();

t.insert('test', 1);
t.insert('tea', 2);
t.insert('ted', 0.5);
t.insert('coffee', 10);
t.insert('covfeffe', 2.3);

console.log(t.find('co'));