How do you add, remove, and update elements in an array?

TL;DR

To add elements to an array, you can use methods like push, unshift, or splice. To remove elements, you can use pop, shift, or splice. To update elements, you can directly access the array index and assign a new value.

let arr = [1, 2, 3];

// Add elements
arr.push(4); // [1, 2, 3, 4]
arr.unshift(0); // [0, 1, 2, 3, 4]
arr.splice(2, 0, 1.5); // [0, 1, 1.5, 2, 3, 4]

// Remove elements
arr.pop(); // [0, 1, 1.5, 2, 3]
arr.shift(); // [1, 1.5, 2, 3]
arr.splice(1, 1); // [1, 2, 3]

// Update elements
arr[1] = 5; // [1, 5, 3]

Adding elements to an array

Using push

The push method adds one or more elements to the end of an array and returns the new length of the array.

let arr = [1, 2, 3];
arr.push(4); // arr is now [1, 2, 3, 4]

Using unshift

The unshift method adds one or more elements to the beginning of an array and returns the new length of the array.

let arr = [1, 2, 3];
arr.unshift(0); // arr is now [0, 1, 2, 3]

Using splice

The splice method can add elements at any position in the array. The first parameter specifies the index at which to start changing the array, the second parameter specifies the number of elements to remove, and the rest are the elements to add.

let arr = [1, 2, 3];
arr.splice(1, 0, 1.5); // arr is now [1, 1.5, 2, 3]

Removing elements from an array

Using pop

The pop method removes the last element from an array and returns that element.

let arr = [1, 2, 3];
arr.pop(); // arr is now [1, 2]

Using shift

The shift method removes the first element from an array and returns that element.

let arr = [1, 2, 3];
arr.shift(); // arr is now [2, 3]

Using splice

The splice method can also remove elements from any position in the array. The first parameter specifies the index at which to start changing the array, and the second parameter specifies the number of elements to remove.

let arr = [1, 2, 3];
arr.splice(1, 1); // arr is now [1, 3]

Updating elements in an array

Direct assignment

You can update elements in an array by directly accessing the index and assigning a new value.

let arr = [1, 2, 3];
arr[1] = 5; // arr is now [1, 5, 3]

Further reading

• MDN Web Docs: Array.prototype.push
• MDN Web Docs: Array.prototype.unshift
• MDN Web Docs: Array.prototype.splice
• MDN Web Docs: Array.prototype.pop
• MDN Web Docs: Array.prototype.shift