What is the difference between array shift and unshift in JavaScript?

Can you explain the difference between array shift and unshift in JavaScript?

Sure! In JavaScript, shift() removes the first element from an array and returns that element, while unshift() adds one or more elements to the beginning of an array and returns the new length of the array.

Can you give me an example of how to use both methods?

Of course! Here's an example:

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

In this example, shift() removes the first element, and unshift() adds a new element at the start.

What happens if I use shift on an empty array?

If you use shift() on an empty array, it will return undefined and the array will remain empty.

Are there any performance differences between the two methods?

Yes, generally, unshift() can be slower than push() because it has to re-index all the elements in the array. shift() can also be slower than pop() for the same reason.