Tuple to Object

Given an array, transform it into an object type and the key/value must be in the provided array.

Tuple is an array with fixed values, e.g. ['tesla', 'model 3', 'model X', 'model Y'].

Example

const tuple = ['tesla', 'model 3', 'model X', 'model Y'] as const

type obj = TupleToObject<typeof tuple> 

/*
expected: 
{ 
    'tesla': 'tesla', 
    'model 3': 'model 3', 
    'model X': 'model X', 
    'model Y': 'model Y'
}
*/

Solution

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

// Example usage:
const tuple = ['tesla', 'model 3', 'model X', 'model Y'] as const

type Result = TupleToObject<typeof tuple>

// Test it:
const result: Result = {
  'tesla': 'tesla',
  'model 3': 'model 3',
  'model X': 'model X',
  'model Y': 'model Y'
}

• T extends readonly PropertyKey[]: This ensures that T is a readonly tuple of property keys
• [K in T[number]]: This creates a new type by iterating over all elements of T
• K: This is the current element of T
• K: This is the value of the key in the resulting object

Playground

Playground

Summary

• Use TupleToObject when you want to transform an array into an object type
• Use cases: Creating an object type from an array of fixed values

References

• Type Challenges: Tuple to Object