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Putting it together

Combine helper functions into a module.

Putting it together

In the final lesson we will add a summary method that combines all helper methods. This method calls capitalize, clamp and formatDate and joins their results in a single string.

Example: helpers.summary = function() { return helpers.capitalize("ready") + " | " + helpers.clamp(15, 0, 10) + " | " + helpers.formatDate("2024-03-15"); }. Call: helpers.summary() returns Ready | 10 | 15.03.2024. This method shows all the library's tools from one place, so you see how the helpers work together. We take the previous lessons' solution and add this method, completing the library.

Summary design

The summary method takes no parameters; it calls all values as hardcoded constants and joins them with the " | " separator. This is a demo method that shows how the library works at a glance.

Flow: helpers.summary = function() { return helpers.capitalize("ready") + " | " + helpers.clamp(15, 0, 10) + " | " + helpers.formatDate("2024-03-15"); }. The call console.log(helpers.summary()) prints Ready | 10 | 15.03.2024. This appears on a new line after the previous outputs (Ready, Hello, 10, 15.03.2024). This way all five lessons' output has accumulated and the helper library is complete.

Practice Add the summary method and call it

Take the previous lessons' solution. Add the helpers.summary method with body return helpers.capitalize("ready") + " | " + helpers.clamp(15, 0, 10) + " | " + helpers.formatDate("2024-03-15");. Print the result with console.log(helpers.summary()).

Starter code

index.js
const helpers = {};
module.exports = helpers;
console.log("Ready");
helpers.capitalize = function(text) {
  if (!text) return text;
  return text[0].toUpperCase() + text.slice(1);
};
console.log(helpers.capitalize("hello"));
helpers.clamp = function(value, min, max) {
  if (value < min) return min;
  if (value > max) return max;
  return value;
};
console.log(helpers.clamp(15, 0, 10));
helpers.formatDate = function(iso) {
  const [y, m, d] = iso.split("-");
  return d + "." + m + "." + y;
};
console.log(helpers.formatDate("2024-03-15"));

// Add the summary method
// write here

// Call summary and print the result
// write here

Sample solution

index.js
const helpers = {};
module.exports = helpers;
console.log("Ready");
helpers.capitalize = function(text) {
  if (!text) return text;
  return text[0].toUpperCase() + text.slice(1);
};
console.log(helpers.capitalize("hello"));
helpers.clamp = function(value, min, max) {
  if (value < min) return min;
  if (value > max) return max;
  return value;
};
console.log(helpers.clamp(15, 0, 10));
helpers.formatDate = function(iso) {
  const [y, m, d] = iso.split("-");
  return d + "." + m + "." + y;
};
console.log(helpers.formatDate("2024-03-15"));
helpers.summary = function() {
  return helpers.capitalize("ready") + " | " + helpers.clamp(15, 0, 10) + " | " + helpers.formatDate("2024-03-15");
};
console.log(helpers.summary());

Expected output

Hazır
Merhaba
10
15.03.2024
Hazır | 10 | 15.03.2024

Questions and answers

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

1 Match each method to its output

Term Meaning
capitalize("hello") Hello
clamp(15, 0, 10) 10
formatDate("2024-03-15") 15.03.2024
summary() All together

2 What does the summary method do?

index.js
helpers.summary()
  • helpers nesnesini siler
  • Only calls capitalize
  • Calls all helpers and joins them into one string Correct answer
  • Adds a new helper

Explanation: summary combines all helpers.

3 Complete the summary call

Question 
console.log(helpers.____());
Answer 
console.log(helpers.summary());

Explanation: summary is called and its result is printed.

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