thenify

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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

$3

Promisifies a function.

$3

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

``js
var thenify = require('thenify');

var somethingAsync = thenify(function somethingAsync(a, b, c, callback) {
callback(null, a, b, c);
});
`

- Backward compatible with callback

`js
var thenify = require('thenify');

var 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 thenify.withCallback()

`js
var thenify = require('thenify').withCallback;

var somethingAsync = thenify(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

`js
var thenify = require('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

`js
var thenify = require('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
// });
// });
``

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[david-url]: https://david-dm.org/thenables/thenify
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[license-url]: LICENSE
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[downloads-url]: https://npmjs.org/package/thenify