How do you get the element type of a Set or Map from a value? const ids = new Set(['a', 'b']); type Id = typeof ids extends Set ? T : never;

With a conditional type using infer on the pattern Set

With indexed access (typeof ids)[number]

With the ElementType utility from the standard library

TypeScript · Senior · Question 31 of 75

How do you get the element type of a `Set<T>` or `Map<K, V>` from a value?

const ids = new Set(['a', 'b']);
type Id = typeof ids extends Set<infer T> ? T : never;

✓Correct answer: With a conditional type using infer on the pattern Set<infer T>
2With indexed access (typeof ids)[number]
3With the ElementType<typeof ids> utility from the standard library

Explanation

Set has no numeric index signature, so [number] doesn't work. A conditional type with infer extracts the parameter of any generic: Map<infer K, infer V>, Promise<infer R>. There's no built-in ElementType utility. Here Id is string.

How do you get the element type of a `Set<T>` or `Map<K, V>` from a value?

Explanation

Further reading

Problem with a question

Test yourself

How do you get the element type of a Set<T> or Map<K, V> from a value?

Explanation

Further reading

Test yourself

How do you get the element type of a `Set<T>` or `Map<K, V>` from a value?