pify

Promisify a callback-style function

Install

$ npm install --save pify

Usage

const fs = require('fs');
const pify = require('pify');

pify(fs.readFile)('package.json', 'utf8').then(data => {
    console.log(JSON.parse(data).name);
    //=> 'pify'
});

// promisify all methods in a module
const promiseFs = pify.all(fs);

promiseFs.readFile('package.json', 'utf8').then(data => {
    console.log(JSON.parse(data).name);
    //=> 'pify'
});

API

pify(input, [promiseModule], [options])

Returns a promise wrapped version of the supplied function.

input

Type: function

Callback-style function.

pify.all(module, [promiseModule], [options])

Returns a version of the module with all its methods promisified.

module

Type: object

Module whose methods you want to promisify.

promiseModule

Type: function

Custom promise module to use instead of the native one.

Check out pinkie-promise if you need a tiny promise polyfill.

options

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.

const request = require('request');
const pify = require('pify');

pify(request, {multiArgs: true})('http://sindresorhus.com').then(result => {
    const [httpResponse, body] = result;
});

include

Type: array

Works for pify.all() only.

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

exclude

Type: array

Works for pify.all() only.

Pick which methods in a module not to promisify.

License

MIT © Sindre Sorhus