trie.js

const words = ['dark', 'dapper'];

let trie = [];

words.forEach(word => {

  addToTrie(word, 0, trie);

});

function addToTrie(word, letterIndex, arrToAddNodeTo) {

  let isEnd = false;
  if (letterIndex == word.length - 1) {
    isEnd = true;
  }

  let newNode;

  for (let i = letterIndex; i < arrToAddNodeTo.length; i++) {
    console.log(arrToAddNodeTo[i].value, word[letterIndex]);
    if (arrToAddNodeTo[i].value == word[letterIndex]) {
      addToTrie(word, ++letterIndex, arrToAddNodeTo);
    } else {
      break;
    }
  }

  if (isEnd) {
    console.log('the end', trie);
    return;
  }

  newNode = {value: word[letterIndex], isEnd, rest: []};
  arrToAddNodeTo.push(newNode);
  addToTrie(word, ++letterIndex, newNode.rest);

}



console.log(JSON.stringify(trie, null, 2));