process.exit and exit codes in Node.js - Cheat Sheet & Quick Revision

Recall & Review

beginner

What does process.exit() do in Node.js?

process.exit() stops the Node.js program immediately. It ends the running process.

beginner

What is an exit code in Node.js?

An exit code is a number that tells the system if the program ended successfully or with an error. 0 means success, any other number means an error or special condition.

beginner

How do you specify an exit code with process.exit()?

You pass the exit code as a number inside the parentheses. For example, process.exit(1) ends the program with exit code 1.

beginner

What does process.exit(0) mean?

process.exit(0) means the program ended successfully without errors.

intermediate

Why should you be careful when using process.exit()?

Because it stops the program immediately, it can skip cleanup tasks like saving files or closing connections. Use it only when you want to end the program right away.

What does process.exit(1) indicate?

A Program ended successfully

B Program ended with an error

C Program paused

D Program restarted

Exit code 1 usually means the program ended with an error or problem.

What happens if you call process.exit() without a number?

A Program continues running

B Program exits with code 1

C Program exits with code 0

D Program throws an error

If no code is given, process.exit() uses 0 by default, meaning success.

Which exit code usually means success?

A -1

B 1

C 100

D 0

Exit code 0 means the program finished successfully.

Why might you avoid using process.exit() in some cases?

A It can skip important cleanup tasks

B It slows down the program

C It causes memory leaks

D It restarts the program

Calling process.exit() stops the program immediately, skipping cleanup like saving data.

How do you end a Node.js program with exit code 2?

A process.exit(2)

B exit(2)

C process.end(2)

D exitCode(2)

You use process.exit(2) to end the program with exit code 2.

Explain what process.exit() does and how exit codes work in Node.js.

Think about how programs tell the system if they ended well or not.

Describe why you should be careful when using process.exit() in your Node.js programs.

Consider what happens if the program stops without finishing important work.

Practice

1. What does process.exit(0) do in a Node.js program?

easy

A. Stops the program immediately and signals success

B. Stops the program immediately and signals an error

C. Pauses the program without exiting

D. Restarts the program automatically

Solution

1. Step 1: Understand process.exit behavior

   process.exit immediately stops the Node.js program.

2. Step 2: Interpret exit code 0

   An exit code of 0 means the program ended successfully without errors.

3. Final Answer:

   Stops the program immediately and signals success -> Option A

4. Quick Check:

   Exit code 0 = success [OK]

Hint: Exit code 0 means success, non-zero means error [OK]

Common Mistakes:

• Thinking exit code 0 means error
• Confusing pause with exit
• Assuming process.exit restarts program

2. Which of the following is the correct syntax to exit a Node.js program with an error code 1?

easy

A. process.exit = 1;

B. exit.process(1);

C. process.exit(1);

D. process.exitCode = 1;

Solution

1. Step 1: Identify correct method to exit

   The method to stop the program is process.exit() with a code inside parentheses.

2. Step 2: Check syntax correctness

   process.exit(1); is the correct syntax to exit with code 1. Other options misuse method or assignment.

3. Final Answer:

   process.exit(1); -> Option C

4. Quick Check:

   Correct method call syntax = process.exit(1); [OK]

Hint: Use process.exit(code) with parentheses to exit [OK]

Common Mistakes:

• Swapping method and object names
• Assigning exit code instead of calling exit()
• Missing parentheses in method call

3. What will be the exit code of this Node.js script?

console.log('Start');
process.exit(2);
console.log('End');

medium

A. Script runs forever

B. 1

C. 0

D. 2

Solution

1. Step 1: Analyze the code flow

   The script prints 'Start', then calls process.exit(2), which stops the program immediately.

2. Step 2: Determine exit code and output

   The exit code is 2. The line printing 'End' never runs.

3. Final Answer:

   2 -> Option D

4. Quick Check:

   process.exit(2) sets exit code 2 [OK]

Hint: Code after process.exit() does not run [OK]

Common Mistakes:

• Assuming all console.logs run
• Confusing exit code with default 0
• Thinking exit code 2 means success

4. Identify the error in this Node.js code snippet:

process.exit = 1;
console.log('Exiting');
process.exit();

medium

A. process.exit is overwritten and no longer a function

B. process.exit() is called correctly with no error

C. Missing exit code argument in process.exit()

D. console.log should come after process.exit()

Solution

1. Step 1: Check assignment to process.exit

   The code assigns 1 to process.exit, replacing the function with a number.

2. Step 2: Understand effect on function call

   Calling process.exit() after overwriting causes an error because it's no longer a function.

3. Final Answer:

   process.exit is overwritten and no longer a function -> Option A

4. Quick Check:

   Overwriting process.exit breaks function call [OK]

Hint: Do not assign values to process.exit, it must stay a function [OK]

Common Mistakes:

• Thinking missing argument causes error
• Assuming console.log runs after exit
• Ignoring that process.exit is a function

5. You want your Node.js script to exit with code 0 if a file exists, or code 3 if it does not. Which code snippet correctly implements this?

import fs from 'fs';
const file = 'data.txt';
if (fs.existsSync(file)) {
  process.exit(0);
} else {
  process.exit(3);
}

hard

A. Throws error because fs.existsSync is asynchronous

B. Correctly exits with 0 if file exists, 3 if not

C. Always exits with 0 regardless of file existence

D. Exits with 3 if file exists, 0 if not

Solution

1. Step 1: Understand fs.existsSync usage

   fs.existsSync checks synchronously if the file exists, returning true or false.

2. Step 2: Check exit codes in if-else

   If file exists, process.exit(0) runs; else process.exit(3) runs. This matches the requirement.

3. Final Answer:

   Correctly exits with 0 if file exists, 3 if not -> Option B

4. Quick Check:

   Sync check + exit codes used correctly [OK]

Hint: Use fs.existsSync for sync check, then process.exit(code) [OK]

Common Mistakes:

• Using async fs.exists instead of sync
• Swapping exit codes in if-else
• Not calling process.exit with parentheses