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Module design

Design the skeleton of the helper library module.

Project: Helper library

In this 5-lesson project you will build a reusable helper library. Each lesson adds one piece, and by the final lesson you will have a working module. All helpers live inside one helpers object.

In Node.js the way to export a module is module.exports. When you write module.exports = helpers, the helpers object becomes available from other files with require. By grouping helpers in an object and exporting it, you create a toolkit usable anywhere in your application. Each lesson's starting code will contain the previous lesson's solution, so the library grows step by step.

The helpers object

First we define an empty helpers object. In the following lessons we will add methods to it. For now we prepare the skeleton and verify it works with console.log.

Example: const helpers = {}; defines the empty object. module.exports = helpers; exports it. console.log("Ready") shows the program runs. module.exports passes a reference, so methods added to helpers later also appear in the exported object. This is the key to growing the library piece by piece.

Practice Define the helpers skeleton

Define an empty object named helpers. Export it with module.exports. Print "Ready" with console.log.

Starter code

index.js
// Define the helpers object
// write here

// Export the module
// write here

// Print "Ready"
// write here

Sample solution

index.js
const helpers = {};
module.exports = helpers;
console.log("Ready");

Expected output

Hazır

Questions and answers

Review the lesson questions together with their answers. To test yourself, solve the lesson interactively.

1 What does module.exports do?

index.js
module.exports = helpers
  • helpers nesnesini siler
  • helpers nesnesini gizler
  • Exports the helpers object Correct answer
  • Renames the helpers object

Explanation: module.exports exposes helpers to other files.

2 Complete the export line

Question 
module.exports = ____;
Answer 
module.exports = helpers;

Explanation: The helpers object is exported.

3 Match each piece to its role

Term Meaning
const helpers = {} Defines an empty object
module.exports Exports
require Imports a module
console.log Prints output

All lessons in Intermediate

1 Events

  1. EventEmitter
  2. on and emit
  3. once
  4. removeListener
  5. error event
  6. Summary - Events

2 Streams

  1. What are streams?
  2. Readable stream
  3. Writable stream
  4. pipe
  5. Transform stream
  6. Summary - Streams

3 HTTP server

  1. http.createServer
  2. Request and response
  3. Routing
  4. JSON response
  5. Query string
  6. Summary - HTTP server

4 Project: Helper library

  1. Module design
  2. String helpers
  3. Number helpers
  4. Date helpers
  5. Putting it together

5 Express basics

  1. What is Express?
  2. express()
  3. app.get
  4. app.post
  5. app.listen
  6. Summary - Express basics

6 Middleware

  1. What is middleware?
  2. app.use
  3. Router middleware
  4. Error middleware
  5. Body parser
  6. Summary - Middleware

7 Routing

  1. Route parameters
  2. Query parameters
  3. express.Router
  4. Route groups
  5. Method chaining
  6. Summary - Routing

8 Project: Quiz app

  1. Quiz model
  2. Adding questions
  3. Running the quiz
  4. Score calculation
  5. Putting it together

9 Async patterns

  1. Async iteration
  2. Async generators
  3. Concurrency limit
  4. Retry pattern
  5. Debounce and throttle
  6. Summary - Async patterns

10 Buffer and binary

  1. What is Buffer?
  2. Buffer.from
  3. Buffer.concat
  4. toString and encoding
  5. Buffer slice
  6. Summary - Buffer

11 Process and CLI

  1. process.argv
  2. process.env
  3. process.exit
  4. process.stdin/stdout
  5. Child process
  6. Summary - Process

12 Project: Library API

  1. Model design
  2. Express app
  3. CRUD routes
  4. Middleware
  5. Putting it together

13 npm and packages

  1. npm install
  2. package.json scripts
  3. devDependencies
  4. Semver
  5. npm publish
  6. Summary - npm

14 Error handling

  1. The Error class
  2. try/catch
  3. Custom errors
  4. Error middleware
  5. Unhandled rejection
  6. Summary - Error handling

15 Testing basics

  1. node:test
  2. assert
  3. describe and it
  4. Before and after
  5. Mock
  6. Summary - Testing basics

16 Debugging

  1. node inspect
  2. Chrome DevTools
  3. console methods
  4. util.inspect
  5. Source maps
  6. Summary - Debugging

17 Date and time

  1. The Date object
  2. Date methods
  3. Intl.DateTimeFormat
  4. performance.now
  5. setTimeout and setInterval
  6. Summary - Date and time

18 Crypto

  1. crypto module
  2. createHash
  3. randomBytes
  4. HMAC
  5. AES
  6. Summary - Crypto

19 URL and query string

  1. URL object
  2. URLSearchParams
  3. URL properties
  4. URL.resolve
  5. querystring
  6. Summary - URL and query string

20 Intermediate final

  1. Project design
  2. Express API
  3. fs persistence
  4. Middleware
  5. Putting it together