value-getter

value-getter

Install

npm install --save value-getter
# or
yarn add value-getter

Usage

import { ValueGetter } from 'value-getter'

const getNodeEnv =
  env('NODE_ENV')
    .required()
    .get()

function env(name: string): ValueGetter<string | undefined> {
  return new ValueGetter(name, () => process.env[name])
}

API

class ValueGetter<T> {
  new (name: string | undefined, get: Getter<T>) => ValueGetter<T>
  new (get: Getter<T>) => ValueGetter<T>

  default<U>(val: U): IValueGetter<AddDefault<T, U>>

  assert<U extends T = T>(
    predicate: (val: T) => boolean
  , message: string
  ): ValueGetter<U>
  assert<U extends T = T>(
    assertion: (val: T) => void
  ): ValueGetter<U>

  required(): IValueGetter<NonNullable<T>>

  memoize(cache:
  | Map<Getter<T>, T>
  | WeakMap<Getter<T>, T>
  ): ValueGetter<T>
  memoize(cacheGetter: Getter<
  | Map<Getter<T>, T>
  | WeakMap<Getter<T>, T>
  >): ValueGetter<T>

  convert<U>(convert: (val: T) => U): IValueGetter<U>

  tap(sideEffect: (val: T) => void): IValueGetter<T>

  get(): Getter<T>

  value(): T
}