The logic here is good, just correct your indentation.  Also, you can see that line 12 is the same as line 18, so the flow can be restructured to combine them:

```
if(index === word.length){
  this.isWord = true;
} else {
  this.characters[char] = this.characters[char] || new Trie();  // Not safe in the compressed trie, you have to use hasOwnProperty or _.has to make sure that you don't think that a key like "constructor" is already filled when it hasn't actually had a key put in there yet.  See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/hasOwnProperty
  this.characters[char].learn(word,index+1);
}
```