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Summary - Debugging

Combine inspect, console and util.inspect to write a debug session.

Summary - Debugging

In this group you learned Node.js's debugging tools: the node inspect terminal debugger, the Chrome DevTools visual interface, console methods, object inspection with util.inspect, and source map mapping to the original source. Now we will combine them in a debugging helper.

Structure: format objects with util.inspect, give general output with console.log, write errors separately with console.error. This is a small example of what a logging helper looks like in a real project. Choosing the right tool during debugging saves time: console.log for quick inspection, DevTools for visual inspection, node inspect for stepping line by line.

Practice Write a debugging helper

Import with const util = require("node:util");. Define const record = { name: "Ayşe", age: 30, grades: [85, 90, 78] };. Define function debugLog(title, data) { console.log(title + ": " + util.inspect(data, { depth: 2, colors: false })); }. Call with debugLog("Record", record). Add console.log("Debugging done").

Starter code

index.js
// Import util
// write here

// Define the record object
// write here

// Define the debugLog function
// write here

// Call debugLog
// write here

// Print "Debugging done"
// write here

Sample solution

index.js
const util = require("node:util");
const record = { name: "Ayşe", age: 30, grades: [85, 90, 78] };
function debugLog(title, data) {
  console.log(title + ": " + util.inspect(data, { depth: 2, colors: false }));
}
debugLog("Record", record);
console.log("Debugging done");

Expected output

Kayıt: { ad: 'Ayşe', yas: 30, notlar: [ 85, 90, 78 ] }
Ayıklama tamam

Questions and answers

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

1 Which tool is best for inspecting a complex object?

index.js
util.inspect(obj, { depth: 3 })
  • Only console.log
  • Only process.exit
  • Formatting with util.inspect and passing it to console.log Correct answer
  • throw new Error

Explanation: util.inspect formats the object readably.

2 Match each tool to its purpose

Term Meaning
node inspect Terminal debugger
DevTools Visual interface
console.error Error stream
util.inspect Object formatting

3 Complete the inspect call

Question 
console.log(util.____(record, { depth: 2 }));
Answer 
console.log(util.inspect(record, { depth: 2 }));

Explanation: util.inspect turns the record object into a string.

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