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path.join

Learn to join paths with path.join.

What is path.join?

path.join joins path segments into a single path. It uses the correct separator for the operating system: \ on Windows, / on Linux and macOS.

import path from 'path';
const p = path.join('folder', 'sub', 'file.txt');
// 'folder/sub/file.txt' (on Linux)

Here three segments are joined into one path. path.join cleans redundant separators; double slashes like 'folder//sub' are fixed automatically. It is the safest way to build paths; always prefer it over manual string concatenation.

path.join examples

path.join works with both relative and absolute segments. If it sees an absolute segment, it ignores everything before it and continues from that absolute path.

path.join('/a', 'b', 'c');   // '/a/b/c'
path.join('a', '/b', 'c');   // '/b/c'

In the first example all segments join in order. In the second, since /b is absolute, 'a' is discarded and the path starts at /b. This means you must be careful building paths dynamically; user input can inject an absolute path with unexpected results.

Practice Your turn: join a path with path.join

Start with import path from 'path'. Write const p = path.join('projects', 'app', 'file.txt'). Log it with console.log(p).

Starter code

index.js
// Import the path module
// Join a path with path.join, log with console.log

Sample solution

index.js
import path from 'path';
const p = path.join('projects', 'app', 'file.txt');
console.log(p);

Expected output

projects/app/file.txt

Questions and answers

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

1 What does path.join('a', 'b', 'c') return?

  • An array
  • A Promise
  • A single joined path Correct answer
  • It throws an error

Explanation: path.join merges segments into a single path.

2 Fill in the blank: path.join

Question 
import path from 'path';
const p = path.____('folder', 'file.txt');
console.log(p);
Answer 
import path from 'path';
const p = path.join('folder', 'file.txt');
console.log(p);

Explanation: You joined segments with path.join.

3 path.join properties

Term Meaning
path.join joins segments
separator OS-specific
absolute segment discards prior

All lessons in Beginner

1 Node.js basics

  1. What is Node.js?
  2. Your first program
  3. ES modules
  4. package.json
  5. CommonJS vs ESM
  6. Summary - Node.js basics

2 Variables

  1. let and const
  2. var and scope
  3. Type inference
  4. Destructuring
  5. Spread and rest
  6. Summary - Variables

3 Data types

  1. Primitive types
  2. Template literals
  3. Number and Math
  4. Symbol
  5. typeof
  6. Summary - Data types

4 Project: Calculator

  1. Project design
  2. Add and subtract
  3. Multiply and divide
  4. process.argv
  5. Putting it together

5 Operators

  1. Arithmetic operators
  2. Assignment operators
  3. Comparison operators
  4. Logical operators
  5. Nullish coalescing
  6. Summary - Operators

6 Strings

  1. String methods
  2. String search
  3. substring and slice
  4. replace and split
  5. padStart and trim
  6. Summary - Strings

7 Conditionals

  1. The if statement
  2. else and else if
  3. switch
  4. Ternary
  5. Optional chaining
  6. Summary - Conditionals

8 Loops

  1. The for loop
  2. The while loop
  3. for...of
  4. for...in
  5. break and continue
  6. Summary - Loops

9 Project: Shopping cart

  1. Cart design
  2. Adding items
  3. Calculating totals
  4. Listing the cart
  5. Putting it together

10 Arrays

  1. Declaring arrays
  2. Array access
  3. push and pop
  4. shift and unshift
  5. splice and slice
  6. Summary - Arrays

11 Array methods

  1. map
  2. filter
  3. reduce
  4. find and some
  5. forEach
  6. Summary - Array methods

12 Objects

  1. Object literal
  2. Property access
  3. Computed properties
  4. Object methods
  5. Object spread
  6. Summary - Objects

13 Functions

  1. Defining functions
  2. Return values
  3. Arrow functions
  4. Default parameters
  5. Rest parameters
  6. Summary - Functions

14 Callbacks

  1. What are callbacks?
  2. Higher-order functions
  3. forEach with callbacks
  4. Error-first callbacks
  5. Callback hell
  6. Summary - Callbacks

15 Project: To-do CLI

  1. Task model
  2. Adding tasks
  3. Listing tasks
  4. Completing tasks
  5. Putting it together

16 Promises

  1. What are promises?
  2. then and catch
  3. Promise.all
  4. Promise.race
  5. finally
  6. Summary - Promises

17 async/await

  1. async function
  2. await
  3. try/catch
  4. await with Promise.all
  5. Sequential await
  6. Summary - async/await

18 fs module

  1. fs.promises
  2. readFile
  3. writeFile
  4. appendFile
  5. existsSync
  6. Summary - fs module

19 path module

  1. path.join
  2. path.resolve
  3. path.parse
  4. path.dirname and basename
  5. path.extname
  6. Summary - path module

20 Beginner final

  1. Project design
  2. Data model
  3. Business logic
  4. fs persistence
  5. Putting it together