Can a string array be transformed into a union type of string literals?

Can we transform this code snippet into something like the following?

  const array = ['a', 'b', 'c']; // this will change dynamically, may sometimes be ['a', 'e', 'f']
  const readonlyArray = array as const;
  type DesiredType = typeof readonlyArray[number];

I believe this might not be achievable, but is there a similar solution that could achieve the same functionality?


Here's a more simplified version of the original problem:

I have a React component with 2 props - status: 'a' | 'b', renamedPropB?: string. When renamedPropB transitions from undefined to, for example, 'Z', the type of status should transition from 'a' | 'b' to 'a' | 'Z'.

The aim is to store the string literals in the union in an array of strings so that it can easily be modified by changing or removing existing string literals from the union.

Answer №1

Applying as const must be done during the creation of the array or object, not afterwards.

If the array originates from an external source, it is unlikely that you can apply as const. The type of elements in the array may be obtained, but if the array is initially created as string[], the element type will be string instead of literal values.

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