https://github.com/HenrikJoreteg/native-promisify-if-present

Return a promise from a callback-as-last-argument function using native a Promise, but only if native Promises exist.
https://github.com/HenrikJoreteg/native-promisify-if-present

Last synced: 9 days ago
JSON representation

Return a promise from a callback-as-last-argument function using native a Promise, but only if native Promises exist.

• Host: GitHub
• URL: https://github.com/HenrikJoreteg/native-promisify-if-present
• Owner: HenrikJoreteg
• Created: 2015-07-08T06:08:16.000Z (over 9 years ago)
• Default Branch: master
• Last Pushed: 2015-07-17T19:52:18.000Z (over 9 years ago)
• Last Synced: 2024-10-31T04:34:52.752Z (12 days ago)
• Language: JavaScript
• Size: 121 KB
• Stars: 17
• Watchers: 2
• Forks: 0
• Open Issues: 1
• Metadata Files:
  • Readme: README.md

Awesome Lists containing this project

README

        
# native-promisify-if-present

Conditionally returns a promise from a callback-as-last-argument function using a native Promise, but only if native Promises exist, and you didn't pass in a callback.

Otherwise your callback function works as usual.

Why another promisify module?! Sorry. Here's why:

1. I'm writing a library and want to support both callbacks and promises

2. I don't want to pick what Promise library you use if you're polyfilling it

3. Since Promises are [part of the web](http://caniuse.com/#feat=promises) now, you should be polyfilling them and using native if present anyway, so this will look for Promises on `window` or `global` if defined.

4. I still don't want it to cause JS errors if you were using the libarary I was building, needing to support IE, and you just want the callback API (even IE 11 doesn't have native promises).

## install

```

npm install native-promisify-if-present

```

## example

```javascript

var promisify = require('native-promisify-if-present');

// write your callback function as usual

function someFunctionThatTakesCallback(name, callback) {

	// if we choose to do this it won't

	// blow up even if there's no native Promises

	// and no callback was passed

	if (!callback) {

		callback = function () {}

	}

	// just error-first your callbacks as usual

	if (somethingWentWrong) {

		callback(new Error('oh crap'))

	} else {

		// error is `null` when successful

		callback(null, 'all is well')	

	}

}

// call promisify to support both mechanisms

module.exports = promisify(someFunctionThatTakesCallback)

```

## credits

If you like this follow [@HenrikJoreteg](http://twitter.com/henrikjoreteg) on twitter.

## license

MIT