text: // Given a binary tree, return the inorder traversal of its nodes' values.
  
  let inorderTraversal = function(root) {
      // variable to hold inorder values
      let values = []
      
      // function to traverse
      let traverse = function(node){
          // check if the node is not null
          if(node){
              // call traverse function and pass in left
              traverse(node.left)
              // push the value
              values.push(node.val)
              // call traverse function and pass in right
              traverse(node.right)
          }
      }
      
      // run traverse function and pass in the root
      traverse(root)
      
      // return in order traversal
      return values
  }
  