Arrays in JavaScript consist of a list of elements. JavaScript has many useful built-in methods to work with arrays. Methods that modify the original array are known as mutator methods, and methods that return a new value or representation are known as accessor methods. In this tutorial, we will focus on accessor methods.

In order to get the most out of this tutorial, you should have some familiarity with creating, indexing, modifying, and looping through arrays, which you can review in the tutorial Understanding Arrays in JavaScript.

This tutorial will go over methods that will concatenate arrays, convert arrays to strings, copy portions of an array to a new array, and find the indices of arrays.

Note: Array methods are properly written out as Array.prototype.method(), as Array.prototype refers to the Array object itself. For simplicity, we will simply list the name as method().

concat()

The concat() method merges two or more arrays together to form a new array.

In the below example, we will create two arrays of types of shellfish and combine them into one new array.

// Create arrays of monovalves and bivalves
let monovalves = ['abalone', 'conch']
let bivalves = ['oyster', 'mussel', 'clam']

// Concatenate them together into shellfish variable
let shellfish = monovalves.concat(bivalves)

shellfish
[ 'abalone', 'conch', 'oyster', 'mussel', 'clam' ]

The concat() method can take multiple arguments, effectively allowing you to concatenate many arrays together with a single method.

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