Record

Functions

lookup

Safely lookup a value in a Record by key, returning an Option.

Examples

Data first style

import { Record, Option } from "@jvlk/fp-tsm"
import { expect } from "jsr:@std/expect"

type T = { a: number | undefined; b: number | null; c?: number }

const record: T = { a: 1, b: null }

const a: Option.Option<number> = Record.lookup(record, "a")
const b: Option.Option<number> = Record.lookup(record, "b")
const c: Option.Option<number> = Record.lookup(record, "c")

expect(a).toEqual(Option.of(1))
expect(b).toEqual(Option.none)
expect(c).toEqual(Option.none)

Pipe style

import { Record, Option, pipe } from "@jvlk/fp-tsm"
import { expect } from "jsr:@std/expect"

type T = { a: number | undefined; b: number | null; c?: number }

const record: T = { a: 1, b: null }

const a: Option.Option<number> = pipe(record, Record.lookup("a"))
const b: Option.Option<number> = Record.lookup(record, "b")
const c: Option.Option<number> = Record.lookup(record, "c")

expect(a).toEqual(Option.of(1))
expect(b).toEqual(Option.none)
expect(c).toEqual(Option.none)