Demo how to write Trie

Trie.js

function TrieNode() {
  this.key = null;
  this.children = {};
  this.isNode = false;
}
function insert(word, r) {
  var start = r;
  for(var index = 0, le = word.length; index<le; index++) {
    if (!start.children.hasOwnProperty(word[index])) {
  	  var t = new TrieNode();
  	  t.key = word[index];
  	  if (index === le - 1) {
  	   t.isNode = true;
  	  }
   	  start.children[word[index]] = t;
    } else {
      if(index === le - 1) {
      	start.isNode = true;
      }
    }
    start = start.children[word[index]];
  }
  return r;
}
function search(word, r) {
  var start = r;
  var isFound;
  if (Object.keys(r).length === 0) {
  	return false;
  }
  for(var j=0, le=word.length; j<le; j++) {
  	if(start.children.hasOwnProperty(word[j])) {
  	  start = start.children[word[j]];
  	  if (j === le - 1 && start.isNode) {
  	  	isFound = true;
  	  } else {
  	  	isFound = false;
  	  }
  	} else {
  		isFound = false;
  		break;
  	}
  }
  return isFound;
}
var sources = ["the", "a", "there", "answer", "any","by", "bye", "their"]; // sources
var root = new TrieNode();
for (var i=0, len = sources.length; i<len; i++) {
  root = insert(sources[i], root); // insert each word
}
search('by', root); // search whether this word exist