AI solution for TypeScript puzzle on BFE.dev
61. implement Prefix<T, P>

To solve this problem, we can use mapped types and template literal types in TypeScript. Here's the implementation:

type Prefix<T, P extends string> = {
  [K in keyof T as `${P}_${K}`]: T[K];
};

Explanation:

1. We define a mapped type Prefix<T, P extends string>.
2. We use the keyof keyword to iterate over all the keys in T.
3. We use the as keyword followed by a template literal type ${P}_${K} to prefix the key names.
4. Inside the square brackets, we map each key K to the new prefixed key ${P}_${K} and its corresponding value T[K].

Now, let's test the implementation:

type A = Prefix<{
  a: 'bfe',
  b: 'dev'
}, 'BFE'>;
// { BFE_a: 'bfe', BFE_b: 'dev'}

// Test case
const a: A = {
  BFE_a: 'bfe',
  BFE_b: 'dev'
};

The type A is expected to be { BFE_a: 'bfe', BFE_b: 'dev'}.

Hope this helps! Let me know if you have any other questions.