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Home > Programming > Data Structures and Algorithms > Learning JavaScript Data Structures and Algorithms
Learning JavaScript Data Structures and Algorithms
Learning JavaScript Data Structures and Algorithms

Learning JavaScript Data Structures and Algorithms: Hone your skills by learning classic data structures and algorithms in JavaScript , Second Edition

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Learning JavaScript Data Structures and Algorithms

Chapter 2. Arrays

An array is the simplest memory data structure. For this reason, all programming languages have a built-in array datatype. JavaScript also supports arrays natively, even though its first version was released without array support. In this chapter, we will dive into the array data structure and its capabilities.

An array stores values sequentially that are all of the same datatype. Although JavaScript allows us to create arrays with values from different datatypes, we will follow best practices and assume that we cannot do this (most languages do not have this capability).

Why should we use arrays?

Let's consider that we need to store the average temperature of each month of the year of the city that we live in. We could use something similar to the following to store this information:

var averageTempJan = 31.9; 
var averageTempFeb = 35.3; 
var averageTempMar = 42.4; 
var averageTempApr = 52; 
var averageTempMay = 60.8;

However, this is not the best approach. If we store the temperature for only one year, we could manage 12 variables. However, what if we need to store the average temperature for more than one year? Fortunately, this is why arrays were created, and we can easily represent the same information mentioned earlier as follows:

var averageTemp = [];
averageTemp[0] = 31.9; 
averageTemp[1] = 35.3; 
averageTemp[2] = 42.4; 
averageTemp[3] = 52; 
averageTemp[4] = 60.8;

We can also represent the averageTemp array graphically:

Why should we use arrays?

Creating and initializing arrays

Declaring, creating, and initializing an array in JavaScript is as simple, as shown by the following:

var daysOfWeek = new Array(); //{1} 
var daysOfWeek = new Array(7); //{2} 
var daysOfWeek = new Array('Sunday', 'Monday', 'Tuesday', 'Wednes day', 'Thursday', 'Friday', 'Saturday'); //{3}

We can simply declare and instantiate a new array using the keyword new (line {1}). Also, using the keyword new, we can create a new array specifying the length of the array (line {2}). A third option would be passing the array elements directly to its constructor (line {3}).

However, using the new keyword is not best practice. If you want to create an array in JavaScript, we can assign empty brackets ([]), as in the following example:

var daysOfWeek = [];

We can also initialize the array with some elements, as follows:

var daysOfWeek = ['Sunday', 'Monday', 'Tuesday', 'Wednesday...

Adding elements

Adding and removing elements from an array is not that difficult; however, it can be tricky. For the examples we will use in this section, let's consider that we have the following numbers array initialized with numbers from 0 to 9:

var numbers = [0,1,2,3,4,5,6,7,8,9];

If we want to add a new element to this array (for example, the number 10), all we have to do is reference the latest free position of the array and assign a value to it:

numbers[numbers.length] = 10;

Note

In JavaScript, an array is a mutable object. We can easily add new elements to it. The object will grow dynamically as we add new elements to it. In many other languages, such as C and Java, we need to determine the size of the array, and if we need to add more elements to the array, we need to create a completely new array; we cannot simply add new elements to it as we need them.

Using the push method

However, there is also a method called push that allows us to add new elements to the end of the array...

Removing elements

So far, you have learned how to add values to the end and at the beginning of an array. Let's take a look at how we can remove a value from an array.

To remove a value from the end of an array, we can use the pop method:

numbers.pop();

Tip

The push and pop methods allow an array to emulate a basic stack data structure, which is the subject of the next chapter.

The output of our array will be the numbers from -4 to 12. The length of our array is 17.

Removing an element from first position

To remove a value from the beginning of the array, we can use the following code:

for (var i=0; i<numbers.length; i++){ 
  numbers[i] = numbers[i+1]; 
}

We can represent the previous code using the following diagram:

Removing an element from first position

We shifted all the elements one position to the left. However, the length of the array is still the same (17), meaning we still have an extra element in our array (with an undefined value). The last time the code inside the loop was executed, i+1 was a reference to a position...

Adding and removing elements from a specific position

So far, you have learned how to add elements at the end and at the beginning of an array, and you have also learned how to remove elements from the beginning and end of an array. What if we also want to add or remove elements from any particular position of our array? How can we do this?

We can use the splice method to remove an element from an array by simply specifying the position/index that we would like to delete from and how many elements we would like to remove, as follows:

numbers.splice(5,3);

This code will remove three elements, starting from index 5 of our array. This means the numbers [5],numbers [6], and numbers [7] will be removed from the numbers array. The content of our array will be -3, -2, -1, 0, 1, 5, 6, 7, 8, 9, 10, 11, and 12 (as the numbers 2, 3, and 4 have been removed).

Note

As with JavaScript arrays and objects, we can also use the delete operator to remove an element from the array, for example, remove numbers...

Why should we use arrays?

Let's consider that we need to store the average temperature of each month of the year of the city that we live in. We could use something similar to the following to store this information:

var averageTempJan = 31.9; 
var averageTempFeb = 35.3; 
var averageTempMar = 42.4; 
var averageTempApr = 52; 
var averageTempMay = 60.8;

However, this is not the best approach. If we store the temperature for only one year, we could manage 12 variables. However, what if we need to store the average temperature for more than one year? Fortunately, this is why arrays were created, and we can easily represent the same information mentioned earlier as follows:

var averageTemp = [];
averageTemp[0] = 31.9; 
averageTemp[1] = 35.3; 
averageTemp[2] = 42.4; 
averageTemp[3] = 52; 
averageTemp[4] = 60.8;

We can also represent the averageTemp array graphically:

Creating and initializing arrays

Declaring, creating, and initializing an array in JavaScript is as simple, as shown by the following:

var daysOfWeek = new Array(); //{1} 
var daysOfWeek = new Array(7); //{2} 
var daysOfWeek = new Array('Sunday', 'Monday', 'Tuesday', 'Wednes day', 'Thursday', 'Friday', 'Saturday'); //{3}

We can simply declare and instantiate a new array using the keyword new (line {1}). Also, using the keyword new, we can create a new array specifying the length of the array (line {2}). A third option would be passing the array elements directly to its constructor (line {3}).

However, using the new keyword is not best practice. If you want to create an array in JavaScript, we can assign empty brackets ([]), as in the following example:

var daysOfWeek = [];

We can also initialize the array with some elements, as follows:

var daysOfWeek = ['Sunday', 'Monday', 'Tuesday', 'Wednesday',  'Thursday', 'Friday', 'Saturday'];

If we want to know how many elements are in the...

Adding elements

Adding and removing elements from an array is not that difficult; however, it can be tricky. For the examples we will use in this section, let's consider that we have the following numbers array initialized with numbers from 0 to 9:

var numbers = [0,1,2,3,4,5,6,7,8,9];

If we want to add a new element to this array (for example, the number 10), all we have to do is reference the latest free position of the array and assign a value to it:

numbers[numbers.length] = 10;

Note

In JavaScript, an array is a mutable object. We can easily add new elements to it. The object will grow dynamically as we add new elements to it. In many other languages, such as C and Java, we need to determine the size of the array, and if we need to add more elements to the array, we need to create a completely new array; we cannot simply add new elements to it as we need them.

Using the push method

However, there is also a method called push that allows us to add new elements to the end of the...

Removing elements

So far, you have learned how to add values to the end and at the beginning of an array. Let's take a look at how we can remove a value from an array.

To remove a value from the end of an array, we can use the pop method:

numbers.pop();

Tip

The push and pop methods allow an array to emulate a basic stack data structure, which is the subject of the next chapter.

The output of our array will be the numbers from -4 to 12. The length of our array is 17.

Removing an element from first position

To remove a value from the beginning of the array, we can use the following code:

for (var i=0; i<numbers.length; i++){ 
  numbers[i] = numbers[i+1]; 
}

We can represent the previous code using the following diagram:

We shifted all the elements one position to the left. However, the length of the array is still the same (17), meaning we still have an extra element in our array (with an undefined value). The last time the code inside the loop was executed, i+1 was a reference...

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Key benefits

  • Understand common data structures and the associated algorithms, as well as the context in which they are used.
  • Master existing JavaScript data structures such as array, set and map and learn how to implement new ones such as stacks, linked lists, trees and graphs.
  • All concepts are explained in an easy way, followed by examples.

Description

This book begins by covering basics of the JavaScript language and introducing ECMAScript 7, before gradually moving on to the current implementations of ECMAScript 6. You will gain an in-depth knowledge of how hash tables and set data structure functions, as well as how trees and hash maps can be used to search files in a HD or represent a database. This book is an accessible route deeper into JavaScript. Graphs being one of the most complex data structures you’ll encounter, we’ll also give you a better understanding of why and how graphs are largely used in GPS navigation systems in social networks. Toward the end of the book, you’ll discover how all the theories presented by this book can be applied in real-world solutions while working on your own computer networks and Facebook searches.

Who is this book for?

If you are a student of Computer Science or are at the start of your technology career and want to explore JavaScript’s optimum ability, this book is for you. You need a basic knowledge of JavaScript and programming logic to start having fun with algorithms.

What you will learn

  • Declare, initialize, add, and remove items from arrays, stacks, and queues
  • Get the knack of using algorithms such as DFS (Depth-first Search) and BFS (Breadth-First Search) for the most complex data structures
  • Harness the power of creating linked lists, doubly linked lists, and circular linked lists
  • Store unique elements with hash tables, dictionaries, and sets
  • Use binary trees and binary search trees
  • Sort data structures using a range of algorithms such as bubble sort, insertion sort, and quick sort

Product Details

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Publication date, Length, Edition, Language, ISBN-13
Publication date : Jun 23, 2016
Length: 314 pages
Edition : 2nd
Language : English
ISBN-13 : 9781785285493
Category :
Programming
Languages :
JavaScript
Concepts :
Data Structures and Algorithms

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Product Details

Publication date : Jun 23, 2016
Length: 314 pages
Edition : 2nd
Language : English
ISBN-13 : 9781785285493
Category :
Programming
Languages :
JavaScript
Concepts :
Data Structures and Algorithms

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Mastering JavaScript Object-Oriented Programming
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Table of Contents

12 Chapters
1. JavaScript—A Quick Overview Chevron down icon Chevron up icon
1. JavaScript—A Quick Overview
JavaScript data structure and algorithms
Setting up the environment
JavaScript basics
Control structures
Functions
Object-oriented programming in Javascript
Debugging and tools
Introducing ECMAScript
ECMAScript 6 functionalities
ECMAScript 7 functionalities
Summary
2. Arrays Chevron down icon Chevron up icon
2. Arrays
Why should we use arrays?
Creating and initializing arrays
Adding elements
Removing elements
Adding and removing elements from a specific position
Two-dimensional and multidimensional arrays
References for JavaScript array methods
The TypedArray class
Summary
3. Stacks Chevron down icon Chevron up icon
3. Stacks
The stack data structure
EcmaScript 6 and the Stack class
Solving problems using stacks
Summary
4. Queues Chevron down icon Chevron up icon
4. Queues
The queue data structure
Creating a queue
The Queue class using ECMAScript 6 syntax
The priority queue
The circular queue - Hot Potato
JavaScript task queues
Summary
5. Linked Lists Chevron down icon Chevron up icon
5. Linked Lists
The linked list data structure
Creating a linked list
Doubly linked lists
Circular linked lists
Summary
6. Sets Chevron down icon Chevron up icon
6. Sets
Structuring a dataset
Creating a set
Set operations
ES6 – the Set class
Summary
7. Dictionaries and Hashes Chevron down icon Chevron up icon
7. Dictionaries and Hashes
Dictionaries
The hash table
The ES6 Map class
The ES6 WeakMap and WeakSet classes
Summary
8. Trees Chevron down icon Chevron up icon
8. Trees
The tree data structure
Tree terminology
The binary and binary search trees
Tree traversal
Searching for values in a tree
Self-balancing trees
Summary
9. Graphs Chevron down icon Chevron up icon
9. Graphs
Graph terminology
Representing a graph
Creating the Graph class
Graph traversals
Shortest path algorithms
Minimum spanning tree (MST)
Summary
10. Sorting and Searching Algorithms Chevron down icon Chevron up icon
10. Sorting and Searching Algorithms
The sorting algorithms
Searching algorithms
Summary
11. Patterns of Algorithm Chevron down icon Chevron up icon
11. Patterns of Algorithm
Recursion
Dynamic programming
Greedy algorithms
Introduction to functional programming
Summary
12. Algorithm Complexity Chevron down icon Chevron up icon
12. Algorithm Complexity
Big-O notation
Having fun with algorithms
Summary

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K Vaidyanathan May 12, 2017
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This book is highly recommended for beginners who really want to implement basic data structures and algorithms from scratch. It is great learning experience.
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Son is very happy with this book
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I bought used and it was in very good conditions. Pretty happy. The book is fantastic and awesome for those like me who wish to learn extra about JS and go deeper.
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The publication date is as accurate as we can be at any point in the project. Unfortunately, delays can happen. Often those delays are out of our control, such as changes to the technology code base or delays in the tech release. We do our best to give you an accurate estimate of the publication date at any given time, and as more chapters are delivered, the more accurate the delivery date will become.

How will I know when new chapters are ready? Chevron down icon Chevron up icon

We'll let you know every time there has been an update to a course that you've bought in Early Access. You'll get an email to let you know there has been a new chapter, or a change to a previous chapter. The new chapters are automatically added to your account, so you can also check back there any time you're ready and download or read them online.

I am a Packt subscriber, do I get Early Access? Chevron down icon Chevron up icon

Yes, all Early Access content is fully available through your subscription. You will need to have a paid for or active trial subscription in order to access all titles.

How is Early Access delivered? Chevron down icon Chevron up icon

Early Access is currently only available as a PDF or through our online reader. As we make changes or add new chapters, the files in your Packt account will be updated so you can download them again or view them online immediately.

How do I buy Early Access content? Chevron down icon Chevron up icon

Early Access is a way of us getting our content to you quicker, but the method of buying the Early Access course is still the same. Just find the course you want to buy, go through the check-out steps, and you’ll get a confirmation email from us with information and a link to the relevant Early Access courses.

What is Early Access? Chevron down icon Chevron up icon

Keeping up to date with the latest technology is difficult; new versions, new frameworks, new techniques. This feature gives you a head-start to our content, as it's being created. With Early Access you'll receive each chapter as it's written, and get regular updates throughout the product's development, as well as the final course as soon as it's ready.We created Early Access as a means of giving you the information you need, as soon as it's available. As we go through the process of developing a course, 99% of it can be ready but we can't publish until that last 1% falls in to place. Early Access helps to unlock the potential of our content early, to help you start your learning when you need it most. You not only get access to every chapter as it's delivered, edited, and updated, but you'll also get the finalized, DRM-free product to download in any format you want when it's published. As a member of Packt, you'll also be eligible for our exclusive offers, including a free course every day, and discounts on new and popular titles.