flags/flags.ts

type FlagHandler = (flag: number) => (flags: number) => number | boolean

const applyFlagHandler = (fn: FlagHandler) => (flags: number) => (initial = 0) => fn(flags)(initial)

const $isset = (flag: number) => (flags = 0): boolean => (flags & flag) === flag
const $set = (flag: number) => (flags = 0): number => flags | flag
const $unset = (flag: number) => (flags = 0): number => flags ^ flag
const $toggle = (flag: number) => (flags = 0): number => $isset(flag)(flags) ? $unset(flag)(flags) : $set(flag)(flags)

const combine = (...options: number[]) => options.reduce((flags, flag) => $set(flag)(flags), 0)
const createMultiFlagHandler = (fn: FlagHandler) => (...options: number[]) => (flags = 0) => applyFlagHandler(fn)(combine(...options))(flags) 

const set = createMultiFlagHandler($set)
const unset = createMultiFlagHandler($unset)
const toggle = createMultiFlagHandler($toggle)
const isset = createMultiFlagHandler($isset)

const settings = set(1, 4, 8)()
console.log(isset(4)(settings))

export {
    combine,
    set,
    unset,
    toggle,
    isset
}