bluebird.md

   1 ---
   2 title: bluebird.js
   3 category: JavaScript libraries
   4 layout: 2017/sheet
   5 weight: -1
   6 updated: 2017-09-08
   7 ---
   8
   9 ### Also see
  10
  11 Also see the [promise cheatsheet](promise.html) and [Bluebird.js API](https://github.com/petkaantonov/bluebird/blob/master/API.md) (github.com).
  12
  13 ### Example
  14
  15 ```js
  16 promise
  17   .then(okFn, errFn)
  18   .spread(okFn, errFn)        // *
  19   .catch(errFn)
  20   .catch(TypeError, errFn)    // *
  21   .finally(fn)
  22   .map(function (e) { ··· })  // *
  23   .each(function (e) { ··· }) // *
  24 ```
  25
  26 Those marked with `*` are non-standard Promise API that only work with Bluebird promises.
  27
  28 ### Multiple return values
  29
  30 ```js
  31 .then(function () {
  32   return [ 'abc', 'def' ]
  33 })
  34 .spread(function (abc, def) {
  35   ···
  36 })
  37 ```
  38 {: data-line="4"}
  39
  40 Use [Promise.spread](http://bluebirdjs.com/docs/api/promise.spread.html)
  41
  42 ### Multiple promises
  43
  44 ```js
  45 Promise.join(
  46   getPictures(),
  47   getMessages(),
  48   getTweets(),
  49   function (pics, msgs, tweets) {
  50     return ···
  51   }
  52 )
  53 ```
  54 {: data-line="1"}
  55
  56 Use [Promise.join](http://bluebirdjs.com/docs/api/promise.join.html)
  57
  58 ### Multiple promises (array)
  59
  60 - [Promise.all](http://bluebirdjs.com/docs/api/promise.all.html)([p]) - expect all to pass
  61 - [Promise.some](http://bluebirdjs.com/docs/api/promise.some.html)([p], count) - expect `count` to pass
  62 - [Promise.any](http://bluebirdjs.com/docs/api/promise.any.html)([p]) - same as `some([p], 1)`
  63 - [Promise.race](http://bluebirdjs.com/docs/api/promise.race.html)([p], count) - use `.any` instead
  64 - [Promise.map](http://bluebirdjs.com/docs/api/promise.map.html)([p], fn, options) - supports concurrency
  65
  66 ```js
  67 Promise.all([ promise1, promise2 ])
  68   .then(results => {
  69     results[0]
  70     results[1]
  71   })
  72
  73 // succeeds if one succeeds first
  74 Promise.any(promises)
  75   .then(results => {
  76   })
  77 ```
  78 {: data-line="1,8"}
  79
  80 ```js
  81 Promise.map(urls, url => fetch(url))
  82   .then(···)
  83 ```
  84 {: data-line="1"}
  85
  86 Use [Promise.map](http://bluebirdjs.com/docs/api/promise.map.html) to "promisify" a list of values.
  87
  88 ### Object
  89
  90 ```js
  91 Promise.props({
  92   photos: get('photos'),
  93   posts: get('posts')
  94 })
  95 .then(res => {
  96   res.photos
  97   res.posts
  98 })
  99 ```
 100 {: data-line="1"}
 101
 102 Use [Promise.props](http://bluebirdjs.com/docs/api/promise.props.html).
 103
 104 ### Chain of promises
 105
 106 ```js
 107 function getPhotos() {
 108   return Promise.try(() => {
 109     if (err) throw new Error("boo")
 110     return result
 111   })
 112 }
 113
 114 getPhotos().then(···)
 115 ```
 116 {: data-line="2"}
 117
 118 Use [Promise.try](http://bluebirdjs.com/docs/api/promise.try.html).
 119
 120 ### Node-style functions
 121
 122 ```js
 123 var readFile = Promise.promisify(fs.readFile)
 124 var fs = Promise.promisifyAll(require('fs'))
 125 ```
 126 {: data-line="2"}
 127
 128 See [Promisification](http://bluebirdjs.com/docs/api/promisification.html).
 129
 130 ### Promise-returning methods
 131
 132 ```js
 133 User.login = Promise.method((email, password) => {
 134   if (!valid)
 135     throw new Error("Email not valid")
 136
 137   return /* promise */
 138 })
 139 ```
 140 {: data-line="1"}
 141
 142 See [Promise.method](http://bluebirdjs.com/docs/api/promise.method.html).
 143
 144 ### Generators
 145
 146 ```js
 147 User.login = Promise.coroutine(function* (email, password) {
 148   let user = yield User.find({email: email}).fetch()
 149   return user
 150 })
 151 ```
 152 {: data-line="1"}
 153
 154 See [Promise.coroutine](http://bluebirdjs.com/docs/api/promise.coroutine.html).
 155
 156 ## Reference
 157
 158 <http://bluebirdjs.com/docs/api-reference.html>