BinarySearchTree.js

/*
- Implement the Node class to create a binary search tree. The constructor should initialize values 'data', 'left', and 'right'.

- Implement the 'insert' method for the Node class. Insert should accept an argument 'data', then create an insert a new node at the appropriate location in the tree.

- Implement the 'contains' method for the Node class. Contains should accept a 'data' argument and return the Node in the tree with the same value.
*/

class Node {
  constructor(data) {
    this.data = data;
    this.left = null;
    this.right = null;
  }
  
  insert(data) {
    if (data < this.data && this.left) {
      this.left.insert(data);
    } else if (data < this.data) {
      this.left = new Node(data);
    } else if (data > this.data && this.right) {
      this.right.insert(data);
    } else if (data > this.data) {
      this.right = new Node(data);
    }
  }
  
  contains(data) {
    if (this.data === data) {
      return this;
    }
    
    if (this.data < data && this.right) {
      return this.right.contains(data);
    } else if (this.data > data && this.left) {
      return this.left.contains(data);
    }
    
    return null;
  }
}

corrected my original contains method

 contains(data) {
    if (this.data == data) {
      return this;
    } else if (this.left && this.left.data === data) {
      return this.left;
    } else if (this.right && this.right.data === data) {
      return this.right;
    } else if (data < this.data && this.left) {
      return this.left.contains(data);
    } else if (data > this.data && this.right) {
      return this.right.contains(data);
    }
    
    return null;
  }