thenify-ex

A fork of thenify to support modern CJS/ESM modules with typescript support.

Promisify a callback-based function using any-promise.

• Preserves function names
• Uses a native promise implementation if available and tries to fall back to a promise implementation such as bluebird
• Converts multiple arguments from the callback into an Array, also support change the behavior by options.multiArgs
• Resulting function never deoptimizes
• Supports both callback and promise style

An added benefit is that thrown errors in that async function will be caught by the promise!

API

fn = thenify(fn, options)

Promisifies a function.

Options

options are optional.

• options.withCallback - support both callback and promise style, default to false.

• options.multiArgs - change the behavior when callback have multiple arguments. default to true.

  • true - converts multiple arguments to an array
  • false- always use the first argument
  • Array - converts multiple arguments to an object with keys provided in options.multiArgs

• Turn async functions into promises

import { thenify } from 'thenify';

const  somethingAsync = thenify(function somethingAsync(a, b, c, callback) {
  callback(null, a, b, c)
})

• Backward compatible with callback

import { thenify } from 'thenify';

const somethingAsync = thenify(
  function somethingAsync(a, b, c, callback) {
    callback(null, a, b, c)
  },
  { withCallback: true },
)

// somethingAsync(a, b, c).then(onFulfilled).catch(onRejected);
// somethingAsync(a, b, c, function () {});

or use withCallback()

import { withCallback}  from "thenify";

var somethingAsync = withCallback(function somethingAsync(a, b, c, callback) {
  callback(null, a, b, c)
})

// somethingAsync(a, b, c).then(onFulfilled).catch(onRejected);
// somethingAsync(a, b, c, function () {});

• Always return the first argument in callback

import { thenify}  from "thenify";

var promise = thenify(
  function (callback) {
    callback(null, 1, 2, 3)
  },
  { multiArgs: false },
)

// promise().then(function onFulfilled(value) {
//   assert.equal(value, 1);
// });

• Converts callback arguments to an object

import { thenify}  from "thenify";

var promise = thenify(
  function (callback) {
    callback(null, 1, 2, 3)
  },
  { multiArgs: ['one', 'tow', 'three'] },
)

// promise().then(function onFulfilled(value) {
//   assert.deepEqual(value, {
//     one: 1,
//     tow: 2,
//     three: 3
//   });
// });