I am presenting the TypeScript code below:
type Item = {
key: number;
value: string;
items?: readonly Item[];
}
const items = [
{ key: 1, value: 'foo', items: [{ key: 3, value: 'baz' }] },
{ key: 2, value: 'bar' }
] as const;
type MyItem = typeof items[number]; // how can this be flattened?
function getItemValue<K extends MyItem['key']>(key: K): Extract<MyItem, { key: K }>['value'];
function getItemValue(key: MyItem['key']) {
return ''; // details of implementation are not necessary.
}
const x = getItemValue(1);
// ^? const x: "foo"
const y = getItemValue(2);
// ^? const x: "bar"
const z = getItemValue(3); // to make it work (it should return 'baz')
// ^?
The purpose of the getItemValue function is to provide the value of the item with the specified key.
It should only allow valid keys and return the correct corresponding value type based on the items array.
I'm focused solely on the typings. The actual implementation of the function is irrelevant. It's working for the main items but not for the nested ones.
Is there a way to flatten the MyItem type?
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