The array is one of the essential Data Structures. In JavaScript, we have many built-in Array methods to manipulate an array. In this article, we will learn how we can add items at the start, middle, and end of a JavaScript Array.

Declaring an empty Array

// We can declare an array using Array() constructor function
const arr = new Array();
// or Simply using an empty square bracket
const arr = [];

Initializing an Array

//  Initializing the array with two integers 3, 4
const arr = new Array(3, 4);
// or
const arr = [3, 4];

Now let's add items to this array.

Adding items at the beginning/start

• We will use the unshift() method for doing this
• You can add any number of items
• You can add not only numbers but also different types of elements other than numbers

arr.unshift(1, 2)
// [1, 2, 3, 4]

Adding items in the middle

• It is slightly tricky😉 but not much complex
• Our current Array, const arr = [1, 2, 3, 4];
• We want to add 7 and 8 in between 2 and 3
• We will use the splice() function for this
• splice() function takes 3 parameters
• First Parameter: Before which position do we want to add
• Second Parameter: How many numbers do we want to delete (We will not use this parameter as we don't want to delete any number now)
• Third Parameter: The items we want to add in the middle
• So, we will keep our second parameter as 0
• After that, we will add the elements we want to add in the middle
• splice(2, 0, 7, 8)
• Before 3, the index of 3 is 2
• 0 as Second Parameter as we don't want to do any delete operation
• We want to add 7, 8 that's why we adding 7, 8 as the last parameter
• You can add as many items as you want
• You can add not only numbers but also different types of elements other than numbers

arr.splice(2, 0, 7, 8);
// Now, the new resultant array will be
// [1, 2, 7, 8, 3, 4]

Adding elements at the end of the array

• This one is simple
• We will use push() operation
• You can add any number of items
• You can add not only numbers but also different types of elements other than numbers

arr.push(5, 6);
// Now, the new resultant array will be
// [1, 2, 7, 8, 3, 4, 5, 6]

All at once

Now let's summarize the article with a single code snippet.

// Declaring an array
const arr = [];
console.log(arr);
// []

# Intializing an array
arr = [3, 4];
console.log(arr);
// [3, 4];

// Adding items at the beginning/ start of the array
arr.unshift(1, 2)
console.log(arr);
// [1, 2, 3, 4]

// Adding items in the middle of the array
arr.splice(2, 0, 7, 8);
console.log(arr);
// [1, 2, 7, 8, 3, 4]

// Adding items at the end of the array
arr.push(5, 6);
console.log(arr);
// [1, 2, 7, 8, 3, 4, 5, 6]

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