This article directly connected with basic tree implementation example, and here you will find some additional methods . All methods did recursively. All of those methods are useful when you want to get a data list, it is a little bit trickier than in linear data structures, but the solution pretty easy.

class Tree {
 .... <- methods which you can find in the previous article

 static inOrder(root) {
    if (root) {
      this.inOrder(root.right)
      console.log(root.value)
      this.inOrder(root.left)
    }
  }

  static postOrder(root) {
    if (root) {
      this.postOrder(root.left)
      this.postOrder(root.right)
      console.log(root.value)
    }
  }

  static preOrder(root) {
    if (root) {
      console.log(root.value)
      this.preOrder(root.left)
      this.preOrder(root.right)
    }
  }
}

... <- tree initialization and adding values, 
also, you can find in prev article

Tree.preOrder(tree) // 20,10,14,40,25
Tree.postOrder(tree) // 14,10,25,40,20
Tree.inOrder(tree) // 40,25,20,14,10