Prateek Budhiraja
Prateek Budhiraja

Prateek Budhiraja

Arrays in JS ๐Ÿš€

Arrays in JS ๐Ÿš€

Learn about Array functions in JS with examples.

Prateek Budhiraja's photo
Prateek Budhiraja
ยทAug 27, 2022ยท

6 min read

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Arrays, as you must know from other programming languages, are used to store a collection of "things", and I am loosely saying "things" here. But here in JavaScript, arrays are a little different and they come with many valuable functions, and in this blog, we'll be looking at those!

Features of Arrays in JS ๐Ÿ’ซ

  • Arrays in JS are not primitive but are objects.
  • Arrays are resizable in JS.
  • They can also store data of different data types, so they are heterogeneous.
  • They follow the indexing rule of 'start with 0'.

๐Ÿ”ต How to Use Arrays ๐Ÿค”

There are many ways to declare and put data in Arrays, some of them are ๐Ÿ‘‡

// Method 1: Using [] and Literals
let continent = [
    "Europe",
    "Asia",
    "Africa",
    "North America",
    "South America",
    "Australia",
    "Antarctica",
];
// Method 2: Using constructor and new keyword
const skills = new Array("JS", "HTML", "CSS", "Tailwind", "Bootstrap");
let score = Array(10);
score = score.fill(0);

console.log(score);

image.png

Now we have our array, but how to get stored data from the array?


๐Ÿ”ต Accessing Values ๐Ÿ“ฆ

If we want to get the whole array, we can just give the array name

// accessing the whole array and printing it on terminal
console.log(continent);
console.log(skills);

image.png

But if we want to get a particular element from the array, we can use [] to access a particular element. And as stated earlier, the index of an array starts from 0, therefore, the first element of the array will be at index 0, the second at index 1 and so on.

console.log(continent[1]);

image.png


๐Ÿ”ต Finding the Length ๐Ÿ“

We can find the length of an Array with .length

let continent = [
    "Europe",
    "Asia",
    "Africa",
    "North America",
    "South America",
    "Australia",
    "Antarctica",
];

console.log("Array length is: ", continent.length);

image.png


๐Ÿ”ต New Array Instance ๐Ÿ†•

๐Ÿ€ Now to create an Array from the previously created array, or from any iterable object, we can do it with Array.from()

// From a available array
let newContinentArray = Array.from(continent);
console.log(newContinentArray);

// From iterable object (string)
let arrayName = Array.from("Prateek Budhiraja");
console.log(arrayName);

image.png

๐Ÿ€ The slice() method returns a copy of a portion of an array into a new array object selected from start-to-end indexes. And the important thing to note here is that the end index is not inclusive.

const animals = ["ant", "dog", "camel", "cat", "elephant"];

console.log(animals.slice(1, 5));
console.log(animals.slice(2, -1));

image.png

๐Ÿ€ The splice() method changes the contents of an array by removing or replacing existing elements and/or adding new elements in place.

console.log(animals);

// syntax: splice(start, deleteCount, item1)
animals.splice(0, 3, "Owl");
console.log(animals);

image.png


๐Ÿ”ต Check If Array โœ”๏ธ

To check if the given name is an array or not, we have Array.isArray()

let continent = [
    "Europe",
    "Asia",
    "Africa",
    "North America",
    "South America",
    "Australia",
    "Antarctica",
];

let country = "India";

console.log("Continent is an array? ", Array.isArray(continent));
console.log("Country is an array? ", Array.isArray(country));

image.png


๐Ÿ”ต Adding and Removing elements from Array โž•โž–

๐Ÿ€ If we want to add/delete elements from the end of the Array (which is also recommended), then we can use push({element}) to insert elements to the array, and pop() to remove the element from the end of the array.

const skills = new Array("JS", "HTML", "CSS", "Tailwind", "Bootstrap");

console.log("Given Array:       ", skills);
skills.pop();
console.log("After pop():       ", skills);
skills.push("React");
console.log("After push(react): ", skills);

image.png

๐Ÿ€ But if we want to insert or remove an element from the start of the array, then we can use unshift({element}) to insert an element at the start or shift(), to delete the element from start.

console.log("Given Array:        ", skills);
skills.shift();
console.log("After shift():      ", skills);
skills.unshift("Node");
console.log("After push(node):   ", skills);

image.png


๐Ÿ”ต Find Inside Array ๐Ÿ”Ž

If we need to find some elements from our array, we have many different functions to do that task.

๐Ÿ€ The find() method returns the first element in the provided array that satisfies the provided testing function. If no values satisfy the testing function, undefined is returned.

let fruitStock = ["Apple", "Pear", "Grapes", "Kiwi", "Cherry", "Pineapple"];

console.log(fruitStock.find((fruit) => fruit === "Apple"));  // checking for "Apple"
console.log(fruitStock.find((fruit) => fruit === "Banana")); // checking for "Banana"

image.png

As it is just showing us undefined in the case of "Banana", we can use a good message by using:

console.log(
    fruitStock.find((fruit) => fruit === "Apple")
        ? "Apple is in Stock!"
        : "Apple is not available!!!"
);

console.log(
    fruitStock.find((fruit) => fruit === "Banana")
        ? "Banana is in Stock!"
        : "Banana is not available!!!"
);

image.png

๐Ÿ€ findIndex() returns the index of the first element in the array that satisfies the provided testing function, or -1 if no appropriate element was found. It is like saying if something exists, where it is.

let fruitStock = ["Apple", "Pear", "Grapes", "Kiwi", "Cherry", "Pineapple"];

console.log(fruitStock.findIndex((fruit) => fruit === "Cherry"));
console.log(fruitStock.findIndex((fruit) => fruit === "Banana"));

image.png

find() and findIndex() finds the first occurrence of the element we provide, but if we want to get the last instance, we can use findLast() and findLastIndex().

๐Ÿ€ findLast() will return the last instance of the element if found and findLastIndex() will returns the index of the last element in the array that satisfies the provided testing function, or -1 if no appropriate element was found.

let laptopInventory = ["HP", "HP", "Dell", "Apple", "Dell", "Apple"];

console.log(laptopInventory.find((laptop) => laptop === "Apple"));
console.log(laptopInventory.findIndex((laptop) => laptop === "Apple"));

image.png

Notice, that it returned 5 instead of 3!

๐Ÿ€ Another very useful function of Array is indexOf(), with this, we can get the index of any element which we specify. We even don't have to give a function to get the result. It returns the index of the element needed and returns -1 if the value is not in the array.

let continent = [
    "Europe",
    "Asia",
    "Africa",
    "North America",
    "South America",
    "Australia",
    "Antarctica",
];

console.log(continent.indexOf("Africa"));
console.log(continent.indexOf("India"));

image.png


๐Ÿ”ต Sorting ๐Ÿ“ถ

let continent = [
    "Europe",
    "Asia",
    "Africa",
    "North America",
    "South America",
    "Australia",
    "Antarctica",
];

continent.sort();
console.log(continent);

image.png


๐Ÿ”ต Reverse

let numbers = [8, 4, 2, 1, -3];

console.log(numbers.reverse());

image.png


๐Ÿ”ต Map

The map function creates a new array and applies the provided function to each of its elements.

let numbers = [8, 4, 2, 1, -3];

let newNumbers = numbers.map((num) => Math.abs(num * 3));

console.log(numbers);
console.log(newNumbers);

image.png


๐Ÿ”ต Filter

The filter() creates a copy of a portion of a given array according to the condition provided.

let foods = ["Apple", "Banana", "Cherry", "Pizza", "Pineapple"];
let fruits = foods.filter((food) => food !== "Pizza");
console.log(fruits);

image.png

I hope you learned something new from this blog, and you'll use some of these methods in your next project.

Happy Learning โœจ

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