A collection of ways for transforming async functions.
📦 Node.js, 🌐 Web, 📜 Files, 📰 JSDoc, 📘 Wiki.

An async function is a function that delivers its result asynchronously (through Promise). This package is an variant of extra-function, and includes methods for transforming async functions. The result of an async function can be manipulated with negate. If a pure async function is expensive, its results can cached with memoize. Parameters of a function can be manipulated with reverse, spread, unspread, wrap, unwrap. reverse flips the order of parameters, spread spreads the first array parameter of a function, unspread combines all parameters into the first parameter (array), wrap adds ignored parameters to the left/right of a function's parameters, and unwrap removes common prefix and suffix parameters to a function (by passing known constant values as prefix/suffix). If you want some functional behavior, compose, composeRight, curry, and curryRight can be used. composeRight is also known as pipe-forward operator or function chaining. If you are unfamiliar, Haskell is a great purely functional language, and there is great haskell beginner guide to learn from.

To control invocation time of a function, use delay. A function can be rate controlled with limitUse, debounce, debounceEarly, throttle, throttleEarly. limitUse controls the number of times a function can be called, and is useful when you want to enforce a function to be called only once, the first n times (before), or after n times. debounce and debounceEarly prevent the invocation of a function during hot periods (when there are too many calls), and can be used for example to issue AJAX request after user input has stopped (for certain delay time). throttle and throttleEarly can be used to limit the rate of invocation of a function, and can be used for example to minimize system usage when a user is constantly refreshing a webpage. Except limitUse, all rate/time control methods can be flushed (flush()) to invoke the target function immediately, or cleared (clear()) to disable invocation of the target function.

In addition, is, signature, name, parameters, and arity obtain metadata (about) information on an async function. To attach a this to a function, use bind. A few generic async functions are also included: SLEEP.

This package is available in both Node.js and Web formats. The web format is exposed as extra_async_function standalone variable and can be loaded from jsDelivr CDN.

Stability: Experimental.

const asyncFunction = require('extra-async-function');
// import * as asyncFunction from "extra-async-function";
// import * as asyncFunction from "https://unpkg.com/extra-async-function/index.mjs"; (deno)

// 1. Basic tests.
async function example1() {
  var a = asyncFunction.composeRight(async x => x*x, async x => x+2);
  await a(10);
  // → 102

  var a = asyncFunction.curry(async (x, y) => x+y);
  await a(2)(3);
  // → 7

  var a = asyncFunction.unspread(async (...xs) => Math.max(...xs));
  await a([2, 3, 1]);
  // → 1.25
}
example1();

• MDN Web docs
• Lodash documentation
• Underscore.js documentation
• Function composition
• Debouncing and Throttling Explained Through Examples by David Corbacho
• Learn You a Haskell for Great Good!: Higher order functions by Miran Lipovaca
• Haskell composition (.) vs F#'s pipe forward operator (|>)
• memoizee package by Mariusz Nowak
• memoizerific package by @thinkloop
• compose-function package by Christoph Hermann
• chain-function package by Jason Quense
• extra-function package by Subhajit Sahu