Essential Books

Promisifying a callback

suggest change

Callback-based: 

db.notification.email.find({subject: 'promisify callback'}, (error, result) => {
   if (error) {
       console.log(error);
   }

   // normal code here
});

This uses bluebird’s promisifyAll method to promisify what is conventionally callback-based code like above. bluebird will make a promise version of all the methods in the object, those promise-based methods names has Async appended to them: 

let email = bluebird.promisifyAll(db.notification.email);

email.findAsync({subject: 'promisify callback'}).then(result => {

    // normal code here
})
.catch(console.error);

If only specific methods need to be promisified, just use its promisify: 

let find = bluebird.promisify(db.notification.email.find);
find({locationId: 168}).then(result => {
    
    // normal code here
});
.catch(console.error);

There are some libraries (e.g., MassiveJS) that can’t be promisified if the immediate object of the method is not passed on second parameter. In that case, just pass the immediate object of the method that need to be promisified on second parameter and enclosed it in context property. 

let find = bluebird.promisify(db.notification.email.find, { context: db.notification.email });
find({locationId: 168}).then(result => {

    // normal code here
});
.catch(console.error);
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Callback to promise:
* Callback to Promise
* Promisifying a callback
* Manually promisifying a callback
* setTimeout promisified
Table Of Contents
0 Getting started
1 npm
2 Web apps with Express
3 Filesystem I/O
4 Exporting and consuming modules
5 Exporting and importing module in node.js
6 Installing Node.js
7 MySQL integration
8 Readline
9 package.json
10 Event emitters
11 Autoreload on changes
12 Environment
13 Callback to promise
14 Executing files or commands with child processes
15 Cluster mode
16 Exception handling
17 Keep a node application constanly running
18 Uninstalling Node.js
19 nvm - Node Version Manager
20 HTTP client and server
21 Using streams
22 Deploying Node.js applications in production
23 Securing node.js application
24 Mongoose library
25 async.js
26 File upload
27 Socket.io communication
28 Mongodb integration
29 Handling POST requests in Node.js
30 Simple REST based CRUD API
31 Template frameworks
32 Node.js architecture inner workings
33 Debugging
34 Node server without a framework
35 Node.js with ES6
36 Interacting with console
37 Cassandra integration
38 Creating APIs with Node.js
39 Graceful shutdown
40 Using IISNode to host Node.js web apps in IIS
41 cli
42 Node.js frameworks
43 grunt
44 Using WebSockets with Node.js
45 metalsmith
46 Parsing command-line arguments
47 Client-server communication
48 Node.js design fundamental
49 Connect to Mongodb
50 Performance challenges
51 Send web notification
52 Remote debugging in node.js
53 MySQL connection pool
54 Database MongoDB with Mongoose
55 Good coding style
56 RESTful API design best practices
57 Deliver HTML or other file
58 TCP Sockets
59 Hack
60 Blueburid promises
61 Async / Await
62 Koa Framework v2
63 Unit testing frameworks
64 ES6
65 Routing AJAX requests with Express.JS
66 Sending a file stream to client
67 Redis
68 Using browserify
69 MongoDB
70 Passport integration
71 Dependency injection
72 Beginner guide
73 Use cases for Node.js
74 Sequelize.js
75 PostgreSQL integration
76 How modules are loaded
77 Oracle DB
78 Synchronous vs. asynchronous
79 Error managemtn
80 Node.js v6 new features
81 Eventloop
82 History of Node.js
83 passport.js
84 Asynchronous programming
85 Stdin / stdout
86 MongoDB
87 Lodash
88 CSV parsing
89 Loopback - REST based connector
90 Running node.js as a service
91 CORS
92 Profiling
93 Performance
94 yarn package manager
95 OAuth 2.0
96 Node.js localization
97 Deploying node.js applications without downtime
98 express.js with angular.js
99 Node.js routing
100 Creating library that supports promises and error-first callbacks
101 MSSQL integration
102 Project structure
103 Avoid callback hell
104 Arduino communication
105 N-API
106 Multi-threading
107 Windows authentication
108 Require
109 Route-controller-service structure
110 Push notifications
111 Contributors