Unshift

Prepend elements to arrays at the type level with Unshift! ⬅️

In this easy-level challenge, you'll implement the type version of Array.unshift in TypeScript. This type takes a tuple and an element, returning a new tuple with the element added at the beginning.

Like its JavaScript counterpart, this type operation demonstrates how to manipulate tuple positions at compile time. You'll solidify your understanding of spread operators and tuple type construction.

For this challenge, you will need to change the following code to make the tests pass (no type check errors).

type Result = Unshift<[1, 2], 0> // [0, 1, 2]

Detailed Explanation

The Unshift type uses the spread operator to prepend an element to a tuple.

type Unshift<T extends unknown[], U> = [U, ...T]

How it works:

• T extends unknown[] ensures T is an array type
• [U, ...T] places U first, then spreads all elements of T
• The result is a new tuple with U at the beginning

This mirrors JavaScript's unshift method perfectly, showing how TypeScript's type system can model array operations with the same intuitive syntax used at runtime.