@kev_nz/async-tools

Async Tools

This is a collection of utility functions for working with async/await code.

Install

npm install @kev_nz/async-tools

API Usage

Here are the functions provided. Additionally feel free to look at the tests in the project as well.

Delay

The delay method allows you to use wait a number of milliseconds before continuing the exection of your code.

const { delay } = require('@kev_nz/async-tools')

(async () => {
  await delay(100)
  console.info('~100 milliseconds later')
})()

Mapper

Execute an asynchronous mapping function over an array of returning the result.

const { mapper } = require('@kev_nz/async-tools')

(async () => {

  const items = [1, 2, 3]
  const mappedItems = await mapper(items, anAsynchronousFunction)
  // passing in an additional concurrency value specifies the number of async methods executed at a time
  const mappedItemsAgain = await mapper(items, anAsynchronousFunction, 2)
})()

Reducer

Execute asynchronous reducer functions over a starting value.

const { delay, reducer } = require('@kev_nz/async-tools')

const anAsyncFunction = async val => {
  await delay(10)
  return val + 1
}
(async () => {
  const finalValue = await reducer(0,
    anAsyncFunction,
    anAsyncFunction,
    anAsyncFunction
  )
  //finalValue 3
})()

Each

Execute an asynchronous function over an array one item at a time.

const { each } = require('@kev_nz/async-tools')

(async () => {
  const items = [1, 2, 3]
  const [first, second, third] = await each(items, anAsyncFunction)
})()

Composer

Take number of functions and compose them together.

const { composer } = require('@kev_nz/async-tools')

const anAsyncFunction = async val => {
  await delay(10)
  return val + 1
}
const anotherAsyncFunction = async val => {
  await delay(10)
  return val + 2
}

(async () => {
  const asyncChain = composer(
    anAsyncFunction,
    anotherAsyncFunction,
    anAsyncFunction
  )
  const finalValue = await asyncChain(0)
  //finalValue 4
})()

Holder

When used with composer it lets you pass additional parameters to a function in the composed.

const { composer, holder } = require('@kev_nz/async-tools')

const anAsyncFunction = async val => {
  await delay(10)
  return val + 1
}
const anotherAsyncFunction = async (val, secondValue) => {
  await delay(10)
  return val + secondValue
}

(async () => {
  const asyncChain = composer(
    anAsyncFunction,
    holder(anotherAsyncFunction, 3),
    anAsyncFunction
  )
  const finalValue = await asyncChain(0)
  //finalValue 5
})()