[JS] Auto-complete feature using Trie

trieAutocomplete.js

// Based on this problem: https://www.geeksforgeeks.org/auto-complete-feature-using-trie/
// We are given a Trie with a set of strings stored in it. Now the user types in a prefix of his search query, we need to give him all recommendations to auto-complete his query based on the strings stored in the Trie. We assume that the Trie stores past searches by the users.
// For example if the Trie store {“abc”, “abcd”, “aa”, “abbbaba”} and the User types in “ab” then he must be shown {“abc”, “abcd”, “abbbaba”}.

function searchAutocomplete(head, prefix) {  
  const words = []; 
  if(!prefix) return words;
  
  let currentNode = head;   
  for(let letter of prefix) {   
    if(currentNode.children && currentNode.children[letter]) { 
      currentNode = currentNode.children[letter]; 
    }
    else {
      return words;
    }
  }
  getWords(currentNode, prefix, words); 

  return words;  
} 

function getWords(node, prefix, words) { 
  if(node.children) { 
    Object.keys(node.children).forEach( letter => { 
      const newWord = prefix + letter;  
      const newNode = node.children[letter];
      getWords(newNode, newWord, words);       
    })
  }
  else words.push(prefix);
}

//------------------------------ Testing ------------------------------------------------//
class Node {
  constructor(value) {
    this.value = value;
    this.children = null; // {'c': NodeC, 'b': NodeB},
  }
}

const root = new Node('*');
const nodeA = new Node('a');
const nodeB = new Node('b');
const nodeF = new Node('f');
const nodeB2 = new Node('b');
const nodeA2 = new Node('a');
const nodeC = new Node('c');
const nodeD = new Node('d');
root.children = { [nodeA.value]: nodeA, [nodeB.value]: nodeB};
nodeA.children = { [nodeF.value]: nodeF, [nodeB2.value]: nodeB2};
nodeB.children = { [nodeA2.value]: nodeA2};
nodeB2.children = { [nodeC.value]: nodeC, [nodeD.value]: nodeD};
//        *
//       / \   
//      a   b
//      /\   \
//     f  b   a
//       / \
//       c  d
console.log( searchAutocomplete(root, "")); // []
console.log( searchAutocomplete(root, "h")); // []
console.log( searchAutocomplete(root, "a")); // [ 'af', 'abc', 'abd' ]
console.log( searchAutocomplete(root, "b")); // [ 'ba' ]
console.log( searchAutocomplete(root, "ab")); // [ 'abc', 'abd' ]