monocle-tsでtraverse

type User = {
    friendNames: string[];
};

const user = {
    friendNames: ["bob", "john"],
};

import { Lens, fromTraversable } from "monocle-ts";
import { array } from "fp-ts/lib/Array";

// Filter and modify the nested array
Lens.fromProp<User>()("friendNames")
    .composeTraverse(fromTraversable(array).filter(n => n === "bob"))
    .modify(n => n.toUpperCase());
// => { friendNames: ["BOB", "john"]}