Tuple to Object

Transform arrays into powerful object types with the Tuple to Object challenge! 🔄

In this easy-level challenge, you'll learn how to convert a tuple (read-only array) into an object type where each array element becomes both a key and its value. This pattern is incredibly useful when working with constant arrays that define allowed values, creating type-safe enums from arrays, or building lookup tables.

You'll explore const assertions, indexed access types, and how TypeScript's type system can transform data structures at the type level. This challenge bridges the gap between runtime values and compile-time types.

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

const tuple = ['tesla', 'model 3', 'model X', 'model Y'] as const
 
type result = TupleToObject<typeof tuple> // expected { 'tesla': 'tesla', 'model 3': 'model 3', 'model X': 'model X', 'model Y': 'model Y'}

Detailed Explanation

To transform a tuple into an object, you need to understand how to iterate over tuple elements and use them as both keys and values.

The solution leverages TypeScript's ability to use tuple elements as keys:

type TupleToObject<T extends readonly PropertyKey[]> = {
  [Key in T[number]]: Key
}

Key concepts:

• T extends readonly PropertyKey[] ensures T is a tuple of valid object keys (string, number, or symbol)
• T[number] accesses all elements in the tuple as a union type
• [Key in T[number]] iterates over each element
• : Key sets the value to be the same as the key

This creates an object where each tuple element appears as both the key and value, perfect for creating lookup tables or enums from constant arrays.