Ternary Binary Tree Implementation in JavaScript

Ternary Binary Tree.js

class Node {
  constructor(char) {
    this.char = char;
    this.right = this.left = this.middle = this.eow = null;
  }
}

class TST {
  constructor() {
    this.root = null;
  }

  add(word) {
    let newNode;
    if (this.root == null) {
      this.addNode(newNode, word, 0);
    } else {
      this.addNode(this.root, word, 0);
    }
  }

  addNode(root, str, index) {
    if (root == null) {
      root = new Node(str[index]);
      if (this.root == null) {
        this.root = root;
      }
    }
    console.log(index, str.length - 1);
    if (index < str.length - 1) {
      if (str[index] < root.char) {
        root.left = this.addNode(root.left, str, index);
      } else if (str[index] > root.char) {
        root.right = this.addNode(root.right, str, index);
      } else {
        root.middle = this.addNode(root.middle, str, index + 1);
      }
    } else root.eow = true;
    return root;
  }
}

(() => {
  let tree = new TST();
  tree.add("Hey!!");
  tree.add("He");
  tree.add("Hey!! I am Ronak Bokaria");
  tree.add("Hey!! I have your notebook");
  console.log(tree);
})();