Consider this:
type Foo = keyof Set<string>
Here, Foo represents the type of all keys in the Set object, e.g. add or delete:
const a: Foo = 'add'; ✅
However, Set also has some well-known symbol properties:
const b: Foo = Symbol.iterator; ✅
However, in a Pick type, how can I reference a symbol key?
type A = Pick<Set<string>, 'add'> ✅
type B = Pick<Set<string>, Symbol.iterator> ❌
The second Pick does not work - "Symbol only refers to a type but is being used as a namespace here."
CodePudding user response：
Symbol.iterator is a value, and you want the type.
type B = Pick<Set<string>, typeof Symbol.iterator>
seems to do the trick.
CodePudding user response：
You can use typeof Symbol.iterator instead:
type pickedIterator = Pick<Set<string>, typeof Symbol.iterator>
// { [Symbol.iterator]: () => IterableIterator<string> }