Arrays in JavaScript

After reading this article you'll be confident using arrays in JavaScript

Need ??

Consider a case when you want to store lots of data e.g. all your favorite pizzas or tacos. How will you store all the names in your program?

Will you create 10 different variables for ten different pizzas? That would be a mess to deal with, So an ARRAY help us to group items together in memory/program under a common name. In simple English say list of pizzas.

So how to use an array?

Let's create an array that will hold the name of our friends we want to invite to our party say, John, Rohan, Mike, Lynda. It looks something like this in js.

let friends = [ 'John', 'Rohan', 'Mike', 'Lynda' ]

The syntax for an array is that it has , separated values inside [ ] square brackets. The values inside it could be of any datatype Number, Boolean, String, Objects, Arrays, etc.

Now we have created an array and we want to access an element from it, how can we do so?? The answer is using indices, every element in an array is associated with an index that is a number, and in javascript, indices start from 0 which means that John will have index 0 and Lynda will have index 3.

For accessing an element we just pass the index of the element we want to access within square brackets in the array.

friends[ 0 ]; // This will return John
friends[ 1 ]; // This will return Rohan
friends[ 2 ]; // This will return Mike
friends[ 3 ]; // This will return Lynda

The friends variable also has a special property named length which holds the length of the array. So,

 console.log( friends.length ) // will print 4 in the console

We can use this property to iterate over the array using a for-loop. Here is an example

let pizzas = [ 'Peppy Paneer', 'Mexican Green Wave', 'Deluxe Veggie', 'Veg Extravaganza', 'CHEESE N CORN' ];

for (let index = 0; index < pizzas.length; index++) {
    console.log( pizzas[ index ] );
/*  this will print all the name */

We can also use the while loop, for-of loop, etc. to iterate over the array. Similarly for changing a value in an array we use the following syntax

let pizzas = [ 'Peppy Paneer', 'Mexican Green Wave', 'Deluxe Veggie', ];
pizzas[0] = "delicious pizza";

So now you have a good understanding of array let us see some array methods that javascript provides us with.

let friends = [ 'John', 'Rohan', 'Mike', 'Lynda' ];

friends.push('The Rock'); /* add The Rock to the end of the array */

friends.pop(); /* removes and returns the last element from the array */

friends.join('*'); /* Joins and return all the element into a string with the provided character */

friends.shift(); /* Removes and returns first element from the array and shifts all the remaining element to a lower index */

friends.unshift('Jake');  /* Adds Jake to the beginning of the array and shifts other elements to a higher index */

There are lots of such methods already given by javascript you can check them out at W3Schools or MDN. Before we wrap up let us see some more example of arrays

let multiDimensionalArray = [ [1, 2, 3], [4, 5, 6], [7, 8, 9] ];
/* As mentioned in the begining arrays can hold any datatype */

let arrayOfObjects = [ 
    { name: 'John', phone: 123654789 },
    { name: 'Lynda', phone: 98756321 },
    { name: 'Rohan', phone: 8852369741 },

let arrayOfEveryThing = [
    "Hello World!!!",
    [ true, false, true, 1, "10" ],
    { name: "John Doe",  age: 25, address: "some address"},,

Well, that's all the basic you need 🎉🎉. In upcoming articles we will see some advanced behavior of our array in JavaScript and how we can use modern syntax to manipulate them.

Avatar for Praveen Kumar

Written by Praveen Kumar

Full Stack @ Quizizz, Google Developer Students Lead, Moderator Codú Community


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