139 lines
2.9 KiB
Markdown
139 lines
2.9 KiB
Markdown
---
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title: bluebird.js
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category: JavaScript libraries
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layout: default-ad
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---
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Also see the [promise cheatsheet](promise.html) and [Bluebird.js API](https://github.com/petkaantonov/bluebird/blob/master/API.md) (github.com).
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{:.center.brief-intro}
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```js
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promise
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.then(okFn, errFn)
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.spread(okFn, errFn) //*
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.catch(errFn)
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.catch(TypeError, errFn) //*
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.finally(fn) //*
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.map(function (e) { ... })
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.each(function (e) { ... })
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```
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----
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### Multiple return values
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Use [Promise.spread](http://bluebirdjs.com/docs/api/promise.spread.html).
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```js
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.then(function () {
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return [ 'abc', 'def' ];
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})
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.spread(function (abc, def) {
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...
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});
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```
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### Multiple promises
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Use [Promise.join](http://bluebirdjs.com/docs/api/promise.join.html).
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```js
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Promise.join(
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getPictures(),
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getMessages(),
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getTweets(),
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function (pics, msgs, tweets) {
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return ...;
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}
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)
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```
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### Multiple promises (array)
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- [Promise.all](http://bluebirdjs.com/docs/api/promise.all.html)([p]) - expect all to pass
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- [Promise.some](http://bluebirdjs.com/docs/api/promise.some.html)([p], count) - expect `count` to pass
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- [Promise.any](http://bluebirdjs.com/docs/api/promise.any.html)([p]) - same as `some([p], 1)`
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- [Promise.race](http://bluebirdjs.com/docs/api/promise.race.html)([p], count) - use `.any` instead
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- [Promise.map](http://bluebirdjs.com/docs/api/promise.map.html)([p], fn, options) - supports concurrency
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```js
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Promise.all([ promise1, promise2 ])
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.then(results => {
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results[0]
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results[1]
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})
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// succeeds if one succeeds first
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Promise.any(promises)
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.then(results => {
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})
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```
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Use [Promise.map](http://bluebirdjs.com/docs/api/promise.map.html) to "promisify" a list of values.
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```js
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Promise.map(urls, url => fetch(url))
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.then(...)
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```
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### Object
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Usually it's better to use `.join`, but whatever.
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```js
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Promise.props({
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photos: get('photos'),
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posts: get('posts')
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})
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.then(res => {
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res.photos
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res.posts
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})
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```
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### Chain of promises
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Use [Promise.try](http://bluebirdjs.com/docs/api/promise.try.html).
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```js
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function getPhotos() {
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return Promise.try(() => {
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if (err) throw new Error("boo")
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return result
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})
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}
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getPhotos().then(...)
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```
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### Using Node-style functions
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See [Promisification](http://bluebirdjs.com/docs/api/promisification.html).
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```js
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var readFile = Promise.promisify(fs.readFile)
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var fs = Promise.promisifyAll(require('fs'))
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```
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### Promise-returning methods
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See [Promise.method](http://bluebirdjs.com/docs/api/promise.method.html).
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```js
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User.login = Promise.method((email, password) => {
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if (!valid)
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throw new Error("Email not valid")
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return /* promise */
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});
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```
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### Generators
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See [Promise.coroutine](http://bluebirdjs.com/docs/api/promise.coroutine.html).
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```
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User.login = Promise.coroutine(function* (email, password) {
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let user = yield User.find({email: email}).fetch()
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return user
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})
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```
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## Reference
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<http://bluebirdjs.com/docs/api-reference.html>
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