• Stars
    star
    1,494
  • Rank 30,008 (Top 0.7 %)
  • Language
    JavaScript
  • License
    MIT License
  • Created over 8 years ago
  • Updated over 1 year ago

Reviews

There are no reviews yet. Be the first to send feedback to the community and the maintainers!

Repository Details

Promisify a callback-style function

pify

Promisify a callback-style function

Install

npm install pify

Usage

import fs from 'fs';
import pify from 'pify';

// Promisify a single function.
const data = await pify(fs.readFile)('package.json', 'utf8');
console.log(JSON.parse(data).name);
//=> 'pify'

// Promisify all methods in a module.
const data2 = await pify(fs).readFile('package.json', 'utf8');
console.log(JSON.parse(data2).name);
//=> 'pify'

API

pify(input, options?)

Returns a Promise wrapped version of the supplied function or module.

input

Type: Function | object

Callback-style function or module whose methods you want to promisify.

options

Type: object

multiArgs

Type: boolean
Default: false

By default, the promisified function will only return the second argument from the callback, which works fine for most APIs. This option can be useful for modules like request that return multiple arguments. Turning this on will make it return an array of all arguments from the callback, excluding the error argument, instead of just the second argument. This also applies to rejections, where it returns an array of all the callback arguments, including the error.

import request from 'request';
import pify from 'pify';

const pRequest = pify(request, {multiArgs: true});

const [httpResponse, body] = await pRequest('https://sindresorhus.com');
include

Type: Array<string | RegExp>

Methods in a module to promisify. Remaining methods will be left untouched.

exclude

Type: Array<string | RegExp>
Default: [/.+(?:Sync|Stream)$/]

Methods in a module not to promisify. Methods with names ending with 'Sync' are excluded by default.

excludeMain

Type: boolean
Default: false

If the given module is a function itself, it will be promisified. Enable this option if you want to promisify only methods of the module.

import pify from 'pify';

function fn() {
	return true;
}

fn.method = (data, callback) => {
	setImmediate(() => {
		callback(null, data);
	});
};

// Promisify methods but not `fn()`.
const promiseFn = pify(fn, {excludeMain: true});

if (promiseFn()) {
	console.log(await promiseFn.method('hi'));
}
errorFirst

Type: boolean
Default: true

Whether the callback has an error as the first argument. You'll want to set this to false if you're dealing with an API that doesn't have an error as the first argument, like fs.exists(), some browser APIs, Chrome Extension APIs, etc.

promiseModule

Type: Function

Custom promise module to use instead of the native one.

FAQ

How is this different from Node.js's util.promisify?

  • Pify existed long before util.promisify.
  • Pify is faster.
  • Pify supports wrapping a whole module/object, not just a specific method.
  • Pify has useful options like the ability to handle multiple arguments (multiArgs).
  • Pify does not have magic behavior for certain Node.js methods and instead focuses on predictability.

How can I promisify a single class method?

Class methods are not bound, so when they're not called on the class itself, they don't have any context. You can either promisify the whole class or use .bind().

import pify from 'pify';
import SomeClass from './some-class.js';

const someInstance = new SomeClass();

// ❌ `someFunction` can't access its class context.
const someFunction = pify(someClass.someFunction);

// ✅ The whole class is promisified and the `someFunction` method is called on its class.
const someClassPromisified = pify(someClass);
someClassPromisified.someFunction();

// ✅ `someFunction` is bound to its class before being promisified.
const someFunction = pify(someClass.someFunction.bind(someClass));

Why is pify choosing the last function overload when using it with TypeScript?

If you're using TypeScript and your input has function overloads, then only the last overload will be chosen and promisified. This is a TypeScript limitation.

If you need to choose a different overload, consider using a type assertion:

function overloadedFunction(input: number, callback: (error: unknown, data: number) => void): void
function overloadedFunction(input: string, callback: (error: unknown, data: string) => void): void {
	/* … */
}

const fn = pify(overloadedFunction as (input: number, callback: (error: unknown, data: number) => void) => void)
//    ^? (input: number) => Promise<number>

Related

  • p-event - Promisify an event by waiting for it to be emitted
  • p-map - Map over promises concurrently
  • More…

More Repositories

1

awesome

😎 Awesome lists about all kinds of interesting topics
270,042
star
2

awesome-nodejs

⚡ Delightful Node.js packages and resources
52,854
star
3

awesome-electron

Useful resources for creating apps with Electron
25,164
star
4

quick-look-plugins

List of useful Quick Look plugins for developers
17,497
star
5

got

🌐 Human-friendly and powerful HTTP request library for Node.js
TypeScript
13,714
star
6

type-fest

A collection of essential TypeScript types
TypeScript
12,930
star
7

pure

Pretty, minimal and fast ZSH prompt
Shell
12,391
star
8

ky

🌳 Tiny & elegant JavaScript HTTP client based on the browser Fetch API
TypeScript
11,367
star
9

pageres

Capture website screenshots
TypeScript
9,573
star
10

ora

Elegant terminal spinner
JavaScript
8,591
star
11

github-markdown-css

The minimal amount of CSS to replicate the GitHub Markdown style
CSS
7,421
star
12

np

A better `npm publish`
JavaScript
7,395
star
13

screenfull

Simple wrapper for cross-browser usage of the JavaScript Fullscreen API
HTML
6,891
star
14

caprine

Elegant Facebook Messenger desktop app
TypeScript
6,816
star
15

Gifski

🌈 Convert videos to high-quality GIFs on your Mac
Swift
6,807
star
16

fkill-cli

Fabulously kill processes. Cross-platform.
JavaScript
6,782
star
17

query-string

Parse and stringify URL query strings
JavaScript
6,453
star
18

execa

Process execution for humans
JavaScript
6,019
star
19

modern-normalize

🐒 Normalize browsers' default style
TypeScript
5,038
star
20

css-in-readme-like-wat

Style your readme using CSS with this simple trick
5,013
star
21

awesome-npm

Awesome npm resources and tips
4,315
star
22

promise-fun

Promise packages, patterns, chat, and tutorials
4,277
star
23

electron-store

Simple data persistence for your Electron app or module - Save and load user preferences, app state, cache, etc
JavaScript
4,165
star
24

awesome-scifi

Sci-Fi worth consuming
4,057
star
25

create-dmg

Create a good-looking DMG for your macOS app in seconds
JavaScript
3,950
star
26

speed-test

Test your internet connection speed and ping using speedtest.net from the CLI
JavaScript
3,882
star
27

ow

Function argument validation for humans
TypeScript
3,779
star
28

eslint-plugin-unicorn

More than 100 powerful ESLint rules
JavaScript
3,765
star
29

file-type

Detect the file type of a Buffer/Uint8Array/ArrayBuffer
JavaScript
3,438
star
30

meow

🐈 CLI app helper
JavaScript
3,305
star
31

p-queue

Promise queue with concurrency control
TypeScript
3,202
star
32

open

Open stuff like URLs, files, executables. Cross-platform.
JavaScript
2,976
star
33

Plash

💦 Make any website your Mac desktop wallpaper
Swift
2,735
star
34

alfy

Create Alfred workflows with ease
JavaScript
2,570
star
35

trash

Move files and directories to the trash
JavaScript
2,512
star
36

fast-cli

Test your download and upload speed using fast.com
JavaScript
2,484
star
37

guides

A collection of succinct guides - Public Domain
2,424
star
38

globby

User-friendly glob matching
JavaScript
2,376
star
39

slugify

Slugify a string
JavaScript
2,357
star
40

emoj

Find relevant emoji from text on the command-line 😮 ✨ 🙌 🐴 💥 🙈
JavaScript
2,311
star
41

cli-spinners

Spinners for use in the terminal
JavaScript
2,255
star
42

on-change

Watch an object or array for changes
JavaScript
1,946
star
43

devtools-detect

Detect if DevTools is open and its orientation
HTML
1,924
star
44

touch-bar-simulator

Use the Touch Bar on any Mac
Swift
1,892
star
45

gulp-imagemin

Minify PNG, JPEG, GIF and SVG images
JavaScript
1,888
star
46

notifier-for-github

Browser extension - Get notified about new GitHub notifications
JavaScript
1,760
star
47

editorconfig-sublime

Sublime Text plugin for EditorConfig - Helps developers maintain consistent coding styles between different editors
Python
1,757
star
48

capture-website

Capture screenshots of websites
JavaScript
1,670
star
49

emittery

Simple and modern async event emitter
JavaScript
1,664
star
50

Defaults

💾 Swifty and modern UserDefaults
Swift
1,661
star
51

electron-boilerplate

Boilerplate to kickstart creating an app with Electron
JavaScript
1,632
star
52

pageres-cli

Capture website screenshots
JavaScript
1,620
star
53

is

Type check values
TypeScript
1,605
star
54

clipboardy

Access the system clipboard (copy/paste)
JavaScript
1,598
star
55

gulp-rev

Static asset revisioning by appending content hash to filenames: `unicorn.css` → `unicorn-d41d8cd98f.css`
JavaScript
1,538
star
56

boxen

Create boxes in the terminal
JavaScript
1,458
star
57

Actions

⚙️ Supercharge your shortcuts
Swift
1,437
star
58

multiline

Multiline strings in JavaScript
JavaScript
1,424
star
59

hyper-snazzy

Elegant Hyper theme with bright colors
JavaScript
1,412
star
60

amas

Awesome & Marvelous Amas
1,392
star
61

LaunchAtLogin

Add “Launch at Login” functionality to your macOS app in seconds
Swift
1,346
star
62

refined-twitter

Browser extension that simplifies the Twitter interface and adds useful features
JavaScript
1,313
star
63

KeyboardShortcuts

⌨️ Add user-customizable global keyboard shortcuts (hotkeys) to your macOS app in minutes
Swift
1,313
star
64

iterm2-snazzy

Elegant iTerm2 theme with bright colors
1,313
star
65

del

Delete files and directories
JavaScript
1,305
star
66

electron-context-menu

Context menu for your Electron app
JavaScript
1,297
star
67

p-limit

Run multiple promise-returning & async functions with limited concurrency
JavaScript
1,294
star
68

Settings

⚙ Add a settings window to your macOS app in minutes
Swift
1,282
star
69

trash-cli

Move files and folders to the trash
JavaScript
1,244
star
70

electron-util

Useful utilities for Electron apps and modules
JavaScript
1,188
star
71

is-online

Check if the internet connection is up
JavaScript
1,181
star
72

ponyfill

🦄 Like polyfill but with pony pureness
1,136
star
73

conf

Simple config handling for your app or module
TypeScript
1,109
star
74

anatine

[DEPRECATED] 🐦 Pristine Twitter app
JavaScript
1,097
star
75

electron-dl

Simplified file downloads for your Electron app
JavaScript
1,087
star
76

log-update

Log by overwriting the previous output in the terminal. Useful for rendering progress bars, animations, etc.
JavaScript
1,027
star
77

pretty-bytes

Convert bytes to a human readable string: 1337 → 1.34 kB
JavaScript
1,022
star
78

grunt-sass

Compile Sass to CSS
JavaScript
1,020
star
79

mem

Memoize functions - an optimization technique used to speed up consecutive function calls by caching the result of calls with identical input
TypeScript
1,019
star
80

DockProgress

Show progress in your app's Dock icon
Swift
1,003
star
81

wallpaper

Manage the desktop wallpaper
JavaScript
996
star
82

p-map

Map over promises concurrently
JavaScript
996
star
83

public-ip

Get your public IP address - very fast!
JavaScript
979
star
84

gulp-app

[DEPRECATED] Gulp as an app
JavaScript
961
star
85

grunt-shell

Run shell commands
JavaScript
952
star
86

load-grunt-tasks

Load multiple grunt tasks using globbing patterns
JavaScript
940
star
87

hasha

Hashing made simple. Get the hash of a buffer/string/stream/file.
JavaScript
934
star
88

pretty-ms

Convert milliseconds to a human readable string: `1337000000` → `15d 11h 23m 20s`
JavaScript
929
star
89

terminal-image

Display images in the terminal
JavaScript
923
star
90

object-assign

ES2015 Object.assign() ponyfill
JavaScript
919
star
91

copy-text-to-clipboard

Copy text to the clipboard in modern browsers (0.2 kB)
JavaScript
858
star
92

System-Color-Picker

🎨 The macOS color picker as an app with more features
Swift
842
star
93

get-port

Get an available TCP port
JavaScript
817
star
94

atom-editorconfig

Helps developers maintain consistent coding styles between different editors
JavaScript
815
star
95

normalize-url

Normalize a URL
JavaScript
807
star
96

grunt-concurrent

Run grunt tasks concurrently
JavaScript
799
star
97

dot-prop

Get, set, or delete a property from a nested object using a dot path
JavaScript
777
star
98

p-progress

Create a promise that reports progress
TypeScript
751
star
99

gulp-changed

Only pass through changed files
JavaScript
747
star
100

generator-nm

Scaffold out a node module
JavaScript
742
star