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Semver

Learn semver and ^/~ version ranges.

Semver

semver (semantic versioning) defines the meaning of version numbers. A version has the form major.minor.patch, for example 4.18.0.

A changing major means a breaking change, a higher minor means a new feature, and a higher patch means a bug fix. When giving a version range in package.json, two symbols are common: ^ (caret) allows updates within the same major; ~ (tilde) allows only patch-level updates. For example ^4.18.0 accepts any version within 4.x; ~4.18.0 accepts only 4.18.x. This way updates are received safely.

Pinning an exact version

Sometimes you want to pin the exact version of a package. Without ^ or ~, writing only 4.18.0 makes npm load just that version; no updates.

This is important for reproducible builds; every install uses the same version. But it also blocks security updates. You can also use wildcards like 1.x or 1.2.x: 1.x accepts any version from 1 up to (but not including) 2. Which range you choose depends on the trade-off between security and stability. Usually ^ is recommended, but in critical systems pinning is safer.

Practice Print the major version

Define a string named version with the value "4.18.0". Take the major part with .split(".")[0] and print it with console.log.

Starter code

index.js
// Define the version string
// Split it on dots
// Print the first part (major)
// write here

Sample solution

index.js
const version = "4.18.0";
const major = version.split(".")[0];
console.log(major);

Expected output

4

Questions and answers

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

1 What does the ^4.18.0 version range allow?

index.js
^4.18.0
  • 4.x (4.18.0 and later 4.x) Correct answer
  • 4.x and 5.x
  • Only 4.18.0
  • Any version

Explanation: ^ allows updates within the same major.

2 Complete the caret range

Question 
"____4.18.0"
Answer 
"^4.18.0"

Explanation: ^4.18.0 allows updates within the same major.

3 Match each range to its behavior

Term Meaning
^1.2.3 Allows minor and patch
~1.2.3 Allows only patch
1.2.3 Pins the exact version
1.x Minor family

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