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https://github.com/shinnn/wrap-promise
Like new Promise(), but prevents implicit rejection
https://github.com/shinnn/wrap-promise
Last synced: 27 days ago
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Like new Promise(), but prevents implicit rejection
- Host: GitHub
- URL: https://github.com/shinnn/wrap-promise
- Owner: shinnn
- License: mit
- Created: 2014-12-13T09:01:50.000Z (almost 10 years ago)
- Default Branch: master
- Last Pushed: 2015-09-12T12:30:04.000Z (about 9 years ago)
- Last Synced: 2024-10-13T17:04:17.986Z (about 1 month ago)
- Language: JavaScript
- Size: 172 KB
- Stars: 1
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
- License: LICENSE
Awesome Lists containing this project
README
# wrap-promise
[](https://www.npmjs.com/package/wrap-promise)
[](https://github.com/shinnn/wrap-promise/releases)
[](https://travis-ci.org/shinnn/wrap-promise)
[](https://ci.appveyor.com/project/ShinnosukeWatanabe/wrap-promise)
[](https://coveralls.io/r/shinnn/wrap-promise)
[](https://david-dm.org/shinnn/wrap-promise)
[](https://david-dm.org/shinnn/wrap-promise#info=devDependencies)
Like `new Promise()`, but prevents implicit rejection
## Comparison
### Using the native `new Promise()`
```javascript
const fs = require('fs');
new Promise((resolve, reject) => {
// Node's fs.readFile throws a type error when the first argument is not a string.
fs.readFile(123, (err, buf) => { // doesn't throw, but calls `onRejected` function
if (err) {
reject(err);
return;
}
resolve(buf);
});
}).catch(() => console.log('This function should be called.'));
```
### Using *wrap-promise*
```javascript
const fs = require('fs');
const wrapPromise = require('wrap-promise');
wrapPromise((resolve, reject) => {
fs.readFile(123, (err, buf) => { // doesn't call `onRejected` but throws immediately
if (err) {
reject(err);
return;
}
resolve(buf);
});
}).catch(() => console.log('This function should not be called.'));
```
[According to the Promise specification](https://github.com/domenic/promises-unwrapping/blob/2a942729249c2490507a1ae6c9a24f8fa11a98e4/reference-implementation/lib/testable-implementation.js#L293-L297), a `promise` will [be rejected implicitly when an error is thrown in the constructor callback](http://www.html5rocks.com/en/tutorials/es6/promises/#toc-exceptions-and-promises). The only (and the biggest) difference is that *wrap-promise* immediately throws an error in such a case.
## Installation
### Package managers
#### [npm](https://www.npmjs.com/)
```
npm install wrap-promise
```
#### [Bower](http://bower.io/)
```
bower install wrap-promise
```
#### [Duo](http://duojs.org/)
```javascript
const wrapPromise = require('shinnn/wrap-promise');
```
### Standalone
[Download the script file directly.](https://raw.githubusercontent.com/shinnn/wrap-promise/master/wrap-promise.js)
## API
### wrapPromise(*fn*)
*fn*: `Function`
Return: `Object` ([Promise](https://promisesaplus.com/))
It can be used in the same way as `new Promise()` but [`new` operator](http://www.ecma-international.org/ecma-262/5.1/#sec-11.2.2) is not needed.
### wrapPromise.Promise
Type: `Function`
Default: global `Promise` or [`require('es6-promise').Promise`](https://github.com/jakearchibald/es6-promise#nodejs)
The `Promise` constructor used in `wrapPromise` function.
#### On [CommonJS](http://www.commonjs.org/)-based environment (e.g. [Node](https://nodejs.org/))
By default it uses the global `Promise` constructor if available, otherwise it [`require`](http://nodejs.org/api/globals.html#globals_require)s [es6-promise](https://github.com/jakearchibald/es6-promise) and use its [`Promise` property](https://github.com/jakearchibald/es6-promise#nodejs).
If you don't need the fallback, use [`no-fallback.js`](https://github.com/shinnn/wrap-promise/blob/master/no-fallback.js) instead. (Useful for [Browserify](http://browserify.org/))
```javascript
const wrapPromise = require('wrap-promise/no-fallback');
```
#### On non-CommonJS environment
It uses the global `Promise` constructor without any fallbacks. Before using `wrapPromise`, you must load `Promise` polyfill if `Promise` doesn't exist by default.
## License
Copyright (c) 2014 - 2015 [Shinnosuke Watanabe](https://github.com/shinnn)
Licensed under [the MIT License](./LICENSE).