Data Structures and Algorithms in JavaScript
This is the coding implementations of the DSA.js book and the repo for the NPM package.
In this repository, you can find the implementation of algorithms and data structures in JavaScript. This material can be used as a reference manual for developers, or you can refresh specific topics before an interview. Also, you can find ideas to solve problems more efficiently.
Table of Contents
Installation
You can clone the repo or install the code from NPM:
npm install dsa.js
and then you can import it into your programs or CLI
const { LinkedList, Queue, Stack } = require('dsa.js');
For a full list of all the exposed data structures and algorithms see.
Features
Algorithms are an essential toolbox for every programmer.
You usually need algorithms when you have to sort data, search for a value, transform data, scale your code to many users, to name a few. Algorithms are just the step you follow to solve a problem while data structures are where you store the data for later manipulation. Both combined create programs.
Algorithms + Data Structures = Programs.
Most programming languages and libraries indeed provide implementations for basic data structures and algorithms. However, to make use of data structures properly, you have to know the tradeoffs so you can choose the best tool for the job.
This material is going to teach you to:

🛠 Apply strategies to tackle algorithm questions. Never to get stuck again. Ace those interviews! 
✂️ Construct efficient algorithms. Learn how to break down problems in manageable pieces.  🧠 Improve your problemsolving skills and become a stronger developer by understanding fundamental computer science concepts.

🤓 Cover essential topics, such as big O time, data structures, and mustknow algorithms. Implement 10+ data structures from scratch.
What's Inside
All the code and explanations are available on this repo. You can dig through the links and code examples from the (src folder). However, the inline code examples are not expanded (because of Github's asciidoc limitations), but you can follow the path and see the implementation.
Note: If you prefer to consume the information more linearly then the book format would be more appropriate for you.
The topics are divided into four main categories as you can see below:
(You can click on the triangle ⯈ to expand the topics)
📈
Algorithms Analysis
Computer Science nuggets without all the mumbojumbo
Computer Science nuggets without all the mumbojumbo
Learn to calculate run time from code examples
Learn how to compare algorithms using Big O notation.
Learn how to compare algorithms using Big O notation.
Comparing algorithms using Big O notation
Let's say you want to find the duplicates on an array. Using Big O notation, we can compare different implementations that do the same but they take different time to complete.
8 examples to explain with code how to calculate time complexity
8 examples to explain with code how to calculate time complexity
Most common time complexities
Time complexity graph
🥞
Linear Data Structures
Understand the ins and outs of the most common data structures.
Understand the ins and outs of the most common data structures
Arrays: Builtin in most languages so not implemented here. Array Time complexity
Linked List: each data node has a link to the next (and previous). Code  Linked List Time Complexity
Queue: data flows in a "firstin, firstout" (FIFO) manner. Code  Queue Time Complexity
Stack: data flows in a "lastin, firstout" (LIFO) manner. Code  Stack Time Complexity
When to use an Array or Linked List. Know the tradeoffs.
When to use an Array or Linked List. Know the tradeoffs
Use Arrays when…
 You need to access data in random order fast (using an index).
 Your data is multidimensional (e.g., matrix, tensor).
 when there is a limit on memory as the requirement of memory is less due to actual data being stored within the index in the array.
Use Linked Lists when:
 You will access your data sequentially.
 You want to save memory and only allocate memory as you need it.
 You want constant time to remove/add from extremes of the list.
 when size requirement is unknown  dynamic size advantage
Build a List, Stack, and a Queue.
Build a List, Stack and a Queue from scratch
Build any of these data structures from scratch:
🌲
NonLinear Data Structures
Understand one of the most versatile data structure of all: Maps
HashMaps
Learn how to implement different types of Maps such as:
Also, learn the difference between the different Maps implementations:
HashMap
is more timeefficient. ATreeMap
is more spaceefficient.TreeMap
search complexity is O(log n), while an optimizedHashMap
is O(1) on average.HashMap
’s keys are in insertion order (or random depending on the implementation).TreeMap
’s keys are always sorted.TreeMap
offers some statistical data for free such as: get minimum, get maximum, median, find ranges of keys.HashMap
doesn’t.TreeMap
has a guarantee always an O(log n), whileHashMap
s has an amortized time of O(1) but in the rare case of a rehash, it would take an O(n).
Know the properties of Graphs and Trees.
Know the properties of Graphs and Trees
Graphs
Know all the graphs properties with many images and illustrations.
Graphs: data nodes that can have a connection or edge to zero or more adjacent nodes. Unlike trees, nodes can have multiple parents, loops. Code  Graph Time Complexity
Trees
Learn all the different kinds of trees and their properties.
Trees: data nodes has zero or more adjacent nodes a.k.a. children. Each node can only have one parent node otherwise is a graph not a tree. Code  Docs
Binary Trees: same as a tree but only can have two children at most. Code  Docs
Binary Search Trees (BST): same as a binary tree, but the nodes value keep this order
left < parent < right
. Code  BST Time complexityAVL Trees: Selfbalanced BST to maximize lookup time. Code  AVL Tree docs  Selfbalancing & tree rotations docs
RedBlack Trees: Selfbalanced BST looser than AVL to maximize insertion speed. Code
Implement a binary search tree for fast lookups.
Implement a binary search tree for fast lookups
From unbalanced BST to balanced BST
1 2 \ / \ 2 => 1 3 \ 3
⚒
Algorithmic Toolbox
Never get stuck solving a problem with 7 simple steps
Never get stuck solving a problem with 8 simple steps
 Understand the problem
 Build a simple example (no edge cases yet)
 Brainstorm solutions (greedy algorithm, Divide and Conquer, Backtracking, brute force)
 Test your answer on the simple example (mentally)
 Optimize the solution
 Write Code, yes, now you can code.
 Test your written code
 Analyse the complexity, both space and time and make sure to optimise further.
Full details here
Master the most popular sorting algorithms (merge sort, quicksort, insertion sort, etc.)
Master the most popular sorting algorithms
We are going to explore three essential sorting algorithms O(n^2), which have low overhead:
and then discuss efficient sorting algorithms O(n log n) such as:
Learn different approaches to solve problems such as divide and conquer, dynamic programming, greedy algorithms, and backtracking.
Learn different approaches to solve algorithmic problems
We are going to discuss the following techniques for solving algorithms problems:
 Greedy Algorithms: makes greedy choices using heuristics to find the best solution without looking back.
 Dynamic Programming: a technique for speeding up recursive algorithms when there are many overlapping subproblems. It uses memoization to avoid duplicating work.
 Divide and Conquer: divide problems into smaller pieces, conquer each subproblem and then join the results.
 Backtracking: search all (or some) possible paths. However, it stops and go back as soon as notice the current solution is not working.
 Brute Force: generate all possible solutions and tries all of them. (Use it as a last resort or as the starting point).
FAQ
How would I apply these to my daytoday work?
As a programmer, we have to solve problems every day. If you want to solve problems well, then it's good to know about a broad range of solutions. A lot of times, it's more efficient to learn existing resources than stumble upon the answer yourself. The more tools and practice you have, the better. This book helps you understand the tradeoffs among data structures and reason about algorithms performance.
Why you created this repo/book?
There are not many books about Algorithms in JavaScript. This material fills the gap. Also, it's good practice :)
Is there anyone I can contact if I have questions about something in particular?
Yes, open an issue or ask questions on the [slack channel](https://dsajsslackin.herokuapp.com).
Book
This project is also available in a book. You will get a nicely formatted PDF with 180+ pages + ePub and Mobi version.
Support
Reach out to me at one of the following places!
 Twitter at
@amejiarosario
 Chat on
dsajs.slack.com