InOrderDFS.js

inOrderDFS(){
    // a variable to store the visited nodes
    let result = []
    // helper function -- accepts a node
    function traverse(node){
        // if node has left, recursion to find the leftest leaf node
     if(node.left) traverse(node.left)
        // push the node to the result
        result.push(node)
        // if node has right, recurstion to find the rightest leaf node
     if(node.right) traverse(node.right) 
    }
    // invoke the helper function with the root
    traverse(root)
  // return the final result
  return result
}