[Trie] Prefix tree for find auto complete suggestions

auto-complete.js

class Node {
  constructor(char) {
    this.char = char;
    this.children = new Map(); // It's limited by 26 chars, hashmap.
    this.isEndWord = false;
  }
}
class Trie {
  constructor() {
    this.root = new Node("");
  }
  insert(...words) {
    // insert the word
    for (const word of words) {
      let node = this.root;
      for (const char of word) {
        if (!node.children.has(char)) {
          node.children.set(char, new Node(char));
        }
        node = node.children.get(char);
      }
      node.isEndWord = true;
    }
  }
  search(word) {
    let found = true;
    let node = this.root;
    for (const char of word) {
      // If we do not have that char in our prefix tree.
      if (!node.children.has(char)) {
        found = false;
        break;
      }
      node = node.children.get(char);
    }
    return node && node.isEndWord && found;
  }
  autocomplete(word) {
    const suggestions = [];
    let node = this.root;
    for (const char of word) {
      if (!node.children.has(char)) {
        return suggestions;
      }
      node = node.children.get(char);
    }
    this.autocompleteHelper(
      node,
      suggestions,
      word.substring(0, word.length - 1)
    );
    return suggestions;
  }
  autocompleteHelper(node, suggestions, prefix) {
    if (node.isEndWord) {
      suggestions.push(prefix + node.char);
    }
    for (const child of node.children.keys()) {
      // in returns key of hashmap.
      const childNode = node.children.get(child);
      this.autocompleteHelper(childNode, suggestions, prefix + node.char);
    }
  }
}

const prefixTree = new Trie();
prefixTree.insert("amz", "am", "amazon");
prefixTree.search("am"); // returns true
console.log(prefixTree.autocomplete("a")); // returns ['am', 'amz', 'amazon']