An Easy Way to Build a Tree in JavaScript Using Object References

Introduction

Let’s say we have a tree data structure. This could be an organizational hierarchy, project breakdown, animal/plant taxonomy, etc. The following is an example of a tree structure:

In an application, it would be fairly common to store this information in the following format, especially if there is a 1-to-many parent/child node relationship:

const data = [
  { id: 56, parentId: 62 },
  { id: 81, parentId: 80 },
  { id: 74, parentId: null },
  { id: 76, parentId: 80 },
  { id: 63, parentId: 62 },
  { id: 80, parentId: 86 },
  { id: 87, parentId: 86 },
  { id: 62, parentId: 74 },
  { id: 86, parentId: 74 },
];

So how would we go from this array-of-objects format into a hierarchical tree format? This actually becomes a fairly easy task when you take advantage JavaScript object references. It can be done without recursion and in O(n) time.

Some Quick Terminology

To make sure we’re speaking the same language, let’s quickly go over some terminology I might use. Each element in our array (i.e., each circle on our tree) is a “node.” A node can be a “parent” of multiple nodes and a “child” of one node. In the picture above, node 86 is the “parent” of node 80 and node 87. node 86 is the “child” of node 74. The top node of our tree is the “root.”

The Overall Methodology

To build our tree, we’re going to want to:

1. Iterate through the data array
2. Find the parent element of the current element
3. In the parent element’s object, add a reference to the child
4. If there is no parent for an element, we know that will be our tree’s “root” element

We must realize that references will be maintained down the object tree, which is why we can accomplish this in O(n) time!

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FreeBSD s3cmd failed [SSL CERTIFICATE_VERIFY_FAILED]

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Updating FreeBSD repository catalogue...
FreeBSD repository is up to date.
All repositories are up to date.
Checking integrity... done (0 conflicting)
The following 8 package(s) will be affected (of 0 checked):

New packages to be INSTALLED:
	libffi: 3.2.1_3
	py37-dateutil: 2.8.1
	py37-magic: 5.38
	py37-s3cmd: 2.1.0
	py37-setuptools: 44.0.0
	py37-six: 1.14.0
	python37: 3.7.8
	readline: 8.0.4

Number of packages to be installed: 8

The process will require 118 MiB more space.

Proceed with this action? [y/N]: y
[rsnapshot] [1/8] Installing readline-8.0.4...
[rsnapshot] [1/8] Extracting readline-8.0.4: 100%
[rsnapshot] [2/8] Installing libffi-3.2.1_3...
....
..
[rsnapshot] [8/8] Extracting py37-s3cmd-2.1.0: 100%
=====
Message from python37-3.7.8:

--
Note that some standard Python modules are provided as separate ports
as they require additional dependencies. They are available as:

py37-gdbm       databases/py-gdbm@py37
py37-sqlite3    databases/py-sqlite3@py37
py37-tkinter    x11-toolkits/py-tkinter@py37

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If sendmail installed remove it. Debian/Ubuntu Linux user type the following apt command/apt-get command:

$`` sudo apt --purge remove sendmail

CentOS/RHEL user type the following yum command or dnf command on Fedora/CentOS/RHEL 8.x:

$`` sudo yum remove sendmail

$`` sudo dnf remove sendmail

Sample outputs from CentOS 8 server:

Dependencies resolved.
===============================================================================
 Package           Architecture  Version               Repository         Size
===============================================================================
Removing:
 sendmail          x86_64        8.15.2-32.el8         @AppStream        2.4 M
Removing unused dependencies:
 cyrus-sasl        x86_64        2.1.27-1.el8          @BaseOS           160 k
 procmail          x86_64        3.22-47.el8           @AppStream        369 k

Transaction Summary
===============================================================================
Remove  3 Packages

Freed space: 2.9 M
Is this ok [y/N]: y

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