Overview

• An array ia a data structure that can hold a collection of values.
• Arrays can contain a mix of different data types, such as numbers, strings, objects, and even other arrays.
• Arrays are resizable You do not have to declare the size of an array before creating it.
• Javascript arrays are zero-indexed meaning the first element is at index 0, the second element is at index 1, and so on. and the insertion order is maintained.
• Arrays are iterables, They can be used in loops, such as for loops, for...of loops, and forEach method.

For e.g.:

const arr = [1,2,3,4,5,6,'Biswas'];
arr.push(7);

for (const item of arr) {
  console.log(item);
}

Which Results the following:

1
2
3
4
5
6
Biswas
7

If you want to add an element at the beginning of the array, you can use the unshift method.

const arr = [1,2,3,4,5,6,'Biswas'];
arr.push(7);
arr.unshift(0);

for (const item of arr) {
  console.log(item);
}

Now you see 0 is the first element of the array.

0
1
2
3
4
5
6
Biswas
7

You can remove an item from end of the array. using arr.pop() Likewsie you can remove an item from beginning of the array. using arr.shift()

For e.g.:

const arr = [1,2,3,4,5,6,'Biswas'];
arr.push(7);
arr.unshift(0);

arr.pop();
arr.shift();

for (const item of arr) {
  console.log(item);
}

Which Results the following:

1
2
3
4
5
6
Biswas

Other methods like map, filter, reduce, concat, slice, spliceare also available.

Array Big-0 Complexity:

• Insert/Remove from the end - O(1)
• Insert/Remove from the beginning - O(n)
• Accessing an element - O(1)
• Searching an element - O(n)
• Push/ Pop - O(1)
• Shift/ Unshift / concat / slice /splice - O(n)
• Foreach / map / filter / reduce - O(n)