Nesting, concat, spread & Array Object Methods

To get you more familiar with arrays, we are going to look at nesting, concatenation and the spread operator

Let's create our fruit array again

const fruits = ["apple", "pear", "orange"];

and let's create a "berries" array

const berries = ["strawberry", "blueberry", "rasberry"];

Now let's nest the berries array inside the fruit array

fruits.push(berries); // ['apples', 'oranges', 'pears', ['strawberries', 'blueberries', 'raspberries']]

Now if we want to access blueberries for example, we can do so

fruits[3][1]; // blueberries

We could also create a new variable and nest both arrays:

const allFruits = [fruits, berries];

allFruits[1][1]; // blueberries

concat()

We may not want to nest arrays, but we can concatenate them together into the same array using concat().

const newArr = fruits.concat(berries); // ['apples', 'oranges', 'pears', 'strawberries', 'blueberries', 'raspberries']

So now we have a single array with all of the values of both arrays. There is no nesting going on.

Spread operator (...)

The spread operator is a very useful operator that allows us to spread out an array into another array. We can use it to achieve the same type of stuff that concat() does. The spread operator also works with object literals, which we will talk about very soon.

const newArr2 = [...fruits, ...berries]; // ['apples', 'oranges', 'pears', 'strawberries', 'blueberries', 'raspberries']

Flatten an array

You can use the flat() method to flatten an array. It takes in a parameter for the depth. If you don't want a limit to the depth, you could use Infinity.

const arr = [1, 2, [3, 4, 5], 6, [7, 8, [9, 10, [11, 12]]]];
x = arr.flat(Infinity);

Static properties on the Array object

The Array object in JavaScript actually has some helpful methods directly associated with it that we can use.

Array.from()

Check if something is an array.

Array.isArray(fruits); // true
Array.isArray("Hello"); // false

Array.from

Convert an array-like object into an array.

Array.from("12345"); // ['1', '2', '3', '4', '5']

Array.of()

Create an array from a variable number of arguments.

const a = 1;
const b = 2;
const c = 3;
y = Array.of(a, b, c); // [1, 2, 3]