process.cwd and __dirname in Node.js - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does process.cwd() return in Node.js?

process.cwd() returns the current working directory from where the Node.js process was started. It shows the folder path you are 'in' when you run your script.

beginner

What is __dirname in Node.js?

__dirname is a variable that holds the directory path of the current JavaScript file. It tells you where the file itself lives on your computer.

intermediate

How do process.cwd() and __dirname differ?

process.cwd() shows the folder where you started the Node.js program.
__dirname shows the folder where the current script file is located.
They can be different if you run the script from another folder.

intermediate

Why might process.cwd() and __dirname be different?

Because you can run a Node.js script from any folder. process.cwd() is where you ran the command, but __dirname is where the script file lives. For example, running node ./scripts/app.js from your home folder means process.cwd() is your home folder, but __dirname is the scripts folder.

beginner

How can you use __dirname to load a file relative to the current script?

<p>You can combine <code>__dirname</code> with <code>path.join()</code> to build a path to a file in the same folder or a subfolder. For example:<br><code>const path = require('path');<br>const filePath = path.join(__dirname, 'data.txt');</code></p>

What does process.cwd() return?

A The folder where the current script file is located

B The user's home directory

C The folder where the Node.js process was started

D The root directory of the system

process.cwd() returns the current working directory where the Node.js process was started.

What does __dirname represent?

A The folder where the Node.js process was started

B The folder where the current script file is located

C The temporary files directory

D The user's home directory

__dirname is the directory path of the current JavaScript file.

If you run node ./scripts/app.js from your home folder, what will process.cwd() return?

A The <code>scripts</code> folder path

B The root folder path

C The <code>app.js</code> file path

D The home folder path

process.cwd() returns the folder where you ran the command, which is the home folder in this case.

Which Node.js module helps safely join paths with __dirname?

A path

B http

C fs

D os

The path module helps join paths safely across different operating systems.

Why is it better to use __dirname instead of process.cwd() when loading files relative to the script?

A Because <code>process.cwd()</code> changes depending on where you run the script

B Because <code>__dirname</code> is always the root folder

C Because <code>process.cwd()</code> is slower

D Because <code>__dirname</code> is a function

process.cwd() depends on where you run the script, so __dirname is more reliable for file paths relative to the script.

Explain the difference between process.cwd() and __dirname in Node.js.

Think about where you run the command vs where the file lives.

How would you use __dirname to load a file named 'config.json' located in the same folder as your script?

Combine __dirname with path.join for safe file paths.

Practice

1. What does process.cwd() return in a Node.js program?

easy

A. The folder where the current script file is located

B. The folder where you started the Node.js program

C. The full path of the current script file

D. The user's home directory

Solution

1. Step 1: Understand process.cwd() purpose

   process.cwd() returns the current working directory where the Node.js process was started, not the script location.

2. Step 2: Compare with __dirname

   __dirname gives the script's folder, which is different from the working directory if you run the script from another folder.

3. Final Answer:

   The folder where you started the Node.js program -> Option B

4. Quick Check:

   process.cwd() = start folder [OK]

Hint: Remember: cwd = where you run node from [OK]

Common Mistakes:

• Confusing process.cwd() with __dirname
• Thinking it returns the script file path
• Assuming it returns the user's home directory

2. Which of the following is the correct way to get the directory name of the current script file in Node.js?

easy

A. __dirname

B. process.dirName

C. process.cwd()

D. currentDir()

Solution

1. Step 1: Identify the built-in variable for script folder

   __dirname is a Node.js global variable that holds the directory path of the current script file.

2. Step 2: Check other options for validity

   process.cwd() returns the working directory, not script folder. The others are not valid Node.js properties or functions.

3. Final Answer:

   __dirname -> Option A

4. Quick Check:

   __dirname = script folder [OK]

Hint: Use __dirname for script folder path [OK]

Common Mistakes:

• Using process.cwd() instead of __dirname
• Trying to use non-existent properties like process.dirName
• Confusing function names

3. Consider this code run from folder /home/user/projects with script located at /home/user/projects/app/server.js:

console.log(process.cwd());
console.log(__dirname);

What will be the output?

medium

A. /home/user/projects
/home/user/projects/app

B. /home/user/projects/app
/home/user/projects/app

C. /home/user/projects/app
/home/user/projects

D. /home/user/projects
/home/user/projects

Solution

1. Step 1: Understand process.cwd() output

   Since the program is started in /home/user/projects, process.cwd() returns this folder.

2. Step 2: Understand __dirname output

   The script is located in /home/user/projects/app/server.js, so __dirname returns /home/user/projects/app.

3. Final Answer:

   /home/user/projects /home/user/projects/app -> Option A

4. Quick Check:

   cwd = start folder, __dirname = script folder [OK]

Hint: cwd = run folder, __dirname = script folder [OK]

Common Mistakes:

• Swapping outputs of process.cwd() and __dirname
• Assuming both return the same path
• Ignoring where the script file is located

4. You wrote this code in /app/index.js and ran it from /app folder:

console.log(process.dirName);

What will happen when you run this script?

medium

A. It prints the current working directory

B. It prints the script's directory

C. It throws a ReferenceError

D. It prints undefined

Solution

1. Step 1: Check the property used

   process.dirName is not a valid property in Node.js. The correct property is __dirname.

2. Step 2: Understand the error caused

   Accessing an undefined property on process does not throw an error, but since process is an object, process.dirName is undefined. However, trying to log undefined prints 'undefined' without error.

3. Step 3: Confirm behavior

   Since process.dirName is undefined, console.log prints 'undefined'. No ReferenceError occurs.

4. Final Answer:

   It prints undefined -> Option D

5. Quick Check:

   Invalid property logs undefined [OK]

Hint: Check exact property names; typos cause undefined [OK]

Common Mistakes:

• Expecting ReferenceError for undefined property
• Confusing __dirname with process.dirName
• Assuming process.dirName exists

5. You want to read a file named config.json located in the same folder as your script /project/src/app.js. You run the script from /project folder. Which code snippet correctly builds the path to config.json to read it safely regardless of where you run the script?

hard

A. const configPath = './config.json';

B. const path = require('path');
const configPath = path.join(process.cwd(), 'config.json');

C. const path = require('path');
const configPath = path.join(__dirname, 'config.json');

D. const configPath = process.cwd() + '/src/config.json';

Solution

1. Step 1: Identify script and file locations

   The script is at /project/src/app.js and config.json is in the same folder /project/src.

2. Step 2: Understand path building with __dirname

   Using __dirname gives the script folder regardless of where you run the script, so joining __dirname with config.json correctly points to the file.

3. Step 3: Analyze other options

   const path = require('path'); const configPath = path.join(process.cwd(), 'config.json'); uses process.cwd() which is /project, so it looks for /project/config.json (wrong folder). const configPath = './config.json'; is relative and depends on run folder, risky. const configPath = process.cwd() + '/src/config.json'; hardcodes path and may break on different OS or run folders.

4. Final Answer:

   const path = require('path'); const configPath = path.join(__dirname, 'config.json'); -> Option C

5. Quick Check:

   Use __dirname to locate files relative to script [OK]

Hint: Use __dirname + path.join for script-relative files [OK]

Common Mistakes:

• Using process.cwd() which depends on run folder
• Using relative paths without __dirname
• Hardcoding paths without path.join