is-async-function

What is is-async-function?

The is-async-function npm package is designed to help developers determine if a given function is an asynchronous function. This can be particularly useful in scenarios where the behavior of code needs to be altered based on whether a function is asynchronous or not, such as in dynamic function execution, middleware handling, or in libraries that need to support both synchronous and asynchronous operations.

What are is-async-function's main functionalities?

Checking if a function is asynchronous

This feature allows you to check if a given function is an async function. The package exports a single function that takes one argument (the function to check) and returns a boolean indicating whether the function is asynchronous. This is useful for dynamically handling functions based on their nature.

const isAsyncFunction = require('is-async-function');

async function foo() {};
console.log(isAsyncFunction(foo)); // true

function bar() {};
console.log(isAsyncFunction(bar)); // false

Other packages similar to is-async-function

is-promise

The is-promise package checks if a value is a Promise, which is a related but different check compared to is-async-function. While is-async-function checks the nature of the function itself, is-promise checks the return value of a function to determine if it's a Promise. This distinction is crucial in understanding and handling asynchronous operations in JavaScript.

kind-of

kind-of is a more general utility for checking the type of a value in JavaScript, which includes support for identifying functions and promises among many other types. Compared to is-async-function, kind-of offers a broader range of type checks but does not specifically focus on distinguishing between synchronous and asynchronous functions. It's more versatile but less specialized.

README

is-async-function

Is function really asynchronous function? Trying to guess that based on check if common-callback-names exists as function arguments names or you can pass your custom.

Install

Install with npm

$ npm i is-async-function --save

Usage

For more use-cases see the tests

const isAsyncFunction = require('is-async-function')

API

isAsyncFunction

Trying to guess is fn asynchronous function or not. But not is-callback-function be aware of that diff.

Example

var fs = require('fs')
var isAsyncFn = require('is-async-function')

console.log(isAsyncFunction(fs.readFile)) // => true
console.log(isAsyncFunction(fs.stat)) // => true

console.log(isAsyncFunction(fs.readFileSync)) // => false
console.log(isAsyncFunction(fs.statSync)) // => false

// or pass custom names to recognize as `async`
console.log(isAsyncFunction(fs.stat, ['cb'])) // => false
console.log(isAsyncFunction(fs.readFile, ['foo', 'bar']))
// => false, because fs.readFile uses `cb`

Params

• fn {Function}: is this fn a callback function
• names {Array}: arguments names, default are common-callback-names
• strict {Boolean}: defaults to true to always return a boolean, pass false to get index (position) - this is useful when you wanna understand which "callback name" exists as argument in that fn
• returns {Boolean|Number}: always boolean true or false when on strict mode, othewise it can be Number index representing the position and if index is 0 it is transformed to boolean true - so always positive value if function is async.

non-strict mode

passing false as second or third argument

var isAsyncFunction = require('is-async-function')

console.log(isAsyncFunction(fs.readFile, false)) // => 2
// => 2, because it callback argument is called `cb`
// and that's the third element in `common-callback-names` array

console.log(isAsyncFunction(fs.stat, false)) // => 1
// => 1, because it callback argument is called `callback_`
// and that's the second element in `common-callback-names` array

Related

• common-callback-names: List of common callback names - callback, cb, callback_, next, done. | homepage
• fn-args: Get the arguments of a function | homepage
• fn-name: Get the name of a named function | homepage
• function-arguments: Get arguments of a function, useful for and used in dependency injectors… more | homepage
• get-fn-name: Get function name with strictness and correctness in mind. Also works for… more | homepage
• is-callback-function: Returns true if function is a callback. Checks its name is one… more | homepage
• parse-function: Parse a function, arrow function or string to object with name, args… more | homepage

Contributing

Pull requests and stars are always welcome. For bugs and feature requests, please create an issue.
But before doing anything, please read the CONTRIBUTING.md guidelines.

Charlike Make Reagent

Changelog

v1.2.1 - 2016-10-27

Fixed

• fix(non-strict): fix a bug in non-strict mode #13

Commits

• chore(release): 1.2.1 f4c7f02