To use an object's value as a generic, you can use the keyof
operator to get the name of the object key as a string literal type. You can then use this string literal type as the generic parameter.
For example, consider the following object:
const obj = {
foo: 'hello',
bar: 42,
};
You can use the keyof
operator to get the keys of the object as a string literal union type:
type ObjKey = keyof typeof obj; // "foo" | "bar"
You can then use this ObjKey
type as the generic parameter:
function getValue<T extends keyof typeof obj>(key: T): typeof obj[T] {
return obj[key];
}
console.log(getValue('foo')); // "hello"
console.log(getValue('bar')); // 42
Asked: 2022-12-14 11:00:00 +0000
Seen: 11 times
Last updated: Jul 15 '21