JavaScript Essentials: Arrays

Essentials is a series that covers the most used and important methods for X topic. It’s a series for developers who know another language or someone who wants a quick start. In this post we cover Arrays.

Table of Contents

— JavaScript Essentials: Arrays
— — Prerequisites
— Array Basics
— — Array Creation
— — Adding / Removing Basics
— Common Methods
— — Modify Every Element in the Array
— — Copy Without Mutating
— — Find the Element(s)/Index
— — Is this Element in the Array?
— — No Duplicates
— — Does Every Item in the Array fulfill these Requirements?
— — Do Some of the Items in the Array fulfill these Requirements?
— — Populate an Array of Emptiness
— — Wtf Sort?
— — How to Reverse a String?
— — Flatten an Array
— — Convert this Array into an Object
— — Loopy Loops
— — Multi-Dimensional Array Manipulation
— — Get the Diagonal ( multi-dimension array )
— References
— More Links
— — Practice

Prerequisites

It’s suggested that you know about Arrow Functions and Ternary expressions before reading. Everything else is just syntax really the focus is on the Array methods.

JavaScript: Arrow Functions for Beginners

JavaScript: What is the ternary operator?

Array Basics

You should know what Arrays are, but just in case here’s a quick overview. Arrays are like boxes that contain stuff inside them, you can remove items, add items or manipulate them. They’re like lists in Python or Arrays in most languages.

Array Creation

Here are a few ways to create Arrays.

Array Creation

Adding / Removing Basics

push pop shift splice

Common Methods

An overview of common scenarios and the method to use for each scenario. You’ll notice most methods that take a callback function have the same parameters: ( element, index, array )

Below are code blocks with a scenario/task described in a comment up top then some code below.

Modify Every Element in the Array

Array.map

Copy Without Mutating

slice, spread

Find the Element(s)/Index

find, findIndex,

Is this Element in the Array?

includes

No Duplicates

unique sets

Does Every Item in the Array fulfill these Requirements?

Array.every

Do Some of the Items in the Array fulfill these Requirements?

Array.some

Populate an Array of Emptiness

Array.fill

Wtf Sort?

Array.sort

How to Reverse a String?

split, reverse, join

Flatten an Array

Experimental Array.flat

Convert this Array into an Object

Array.reduce

Loopy Loops

for in, for of, forEach, Array.entries

Multi-Dimensional Array Manipulation

Multi-Dimension Array Manipulation

Get the Diagonal ( multi-dimension array )

multi-dimension array, diagonal, reduce

References

Array

Set

More Links

More resources and cool things to check out.

JavaScript Array Explorer

JavaScript Essentials

Practice

Challenges on CodeWars ( easier ones are listed first up top )

Sum of positive

Remove the minimum

Array.diff

Thanks for reading! Leave any feedback in the comments and let me know if there’s a better way to structure these posts ( updated to use Carbon instead of Medium code blocks )

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