Are you using the returned value? TL;DR: Avoid assigning values you never use. Problems Dead code
Unclear intent
Maintenance overhead
Hidden complexity
Debugging leftovers
Bad scoping
Commented code
Mutability Solutions Remove unused assignments.
Try to avoid side effects. Context When you assign a value to a local variable but never use it, you create unnecessary clutter in your code. This can confuse others and make the code harder to maintain. Sometimes, when debugging you can assign temporal variables for better inspection. This also happens when you assign the execution to an object property but it is harder to follow. It is also a sign of a mutating object because if you remove the assignment, only the side effects remain. Mutating objects can cause unexpected side effects, making it harder to track changes. Sample Code Wrong function updateUserName(user, newname) {
  user.name = newname;
  return user;
}

function performMaintenance(existingUser) {
  let updatedUser = updateUserName(existingUser, "Bobby Peru");
  // Other tasks
}
// The variable updatedUser is never used Right function updateUserName(user, newname) {
  user.name = newname;
  // Just side effects without explicit return
}

function performMaintenance(existingUser) {
  updateUserName(existingUser, "Bobby Peru");
  // Other tasks
} Detection [x]Automatic You can detect this smell using static analysis tools or code reviews that check for unused variables after assignment. Most linters flag this as an issue. Tags Bloaters Level [x]Beginner Why the Bijection Is Important It stays clean and efficient when your code accurately reflects real-world logic. Unused assignments break this connection, making it harder to understand the intent and maintain the code. AI Generation AI tools seldom generate unused variable assignments when they misunderstand intent. AI Detection AI-assisted refactoring with clear instructions can flag unused variables and suggest removals, but it might not always understand if the return value should have been used. Try Them! Remember: AI Assistants make lots of mistakes Without Proper Instructions

With Specific Instructions



ChatGPT

ChatGPT



Claude

Claude



Perplexity

Perplexity



Copilot

Copilot



Gemini

Gemini



DeepSeek

DeepSeek



Meta AI

Meta AI Conclusion Unused variables after mutations create noise and confusion. Don't assign the return value if you don't need it. If the method should return something meaningful, make sure you use it. Relations https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xlii?embedable=true https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xxxvi?embedable=true https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xxxi?embedable=true https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xxii?embedable=true More Information https://hackernoon.com/is-it-crystal-clear-for-everybody-that-a-date-should-not-mutate-wuoy3z03?embedable=true Disclaimer Code Smells are my opinion. Credits Photo by Evan Demicoli on Unsplash If you have to spend effort to decipher code, you should rewrite it. Martin Golding https://hackernoon.com/400-thought-provoking-software-engineering-quotes?embedable=true This article is part of the CodeSmell Series. https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-i-xqz3evd?embedable=true Are you using the returned value? Are you using the returned value? TL;DR: Avoid assigning values you never use. TL;DR: Avoid assigning values you never use. Problems Dead code Unclear intent Maintenance overhead Hidden complexity Debugging leftovers Bad scoping Commented code Mutability Dead code Unclear intent Maintenance overhead Maintenance overhead Hidden complexity Debugging leftovers Bad scoping scoping Commented code Mutability Mutability Solutions Remove unused assignments. Try to avoid side effects. Remove unused assignments. Try to avoid side effects . side effects Context When you assign a value to a local variable but never use it, you create unnecessary clutter in your code. local variable This can confuse others and make the code harder to maintain. Sometimes, when debugging you can assign temporal variables for better inspection. This also happens when you assign the execution to an object property but it is harder to follow. object property It is also a sign of a mutating object because if you remove the assignment, only the side effects remain. mutating object Mutating objects can cause unexpected side effects, making it harder to track changes. Sample Code Wrong function updateUserName(user, newname) {
  user.name = newname;
  return user;
}

function performMaintenance(existingUser) {
  let updatedUser = updateUserName(existingUser, "Bobby Peru");
  // Other tasks
}
// The variable updatedUser is never used function updateUserName(user, newname) {
  user.name = newname;
  return user;
}

function performMaintenance(existingUser) {
  let updatedUser = updateUserName(existingUser, "Bobby Peru");
  // Other tasks
}
// The variable updatedUser is never used Right function updateUserName(user, newname) {
  user.name = newname;
  // Just side effects without explicit return
}

function performMaintenance(existingUser) {
  updateUserName(existingUser, "Bobby Peru");
  // Other tasks
} function updateUserName(user, newname) {
  user.name = newname;
  // Just side effects without explicit return
}

function performMaintenance(existingUser) {
  updateUserName(existingUser, "Bobby Peru");
  // Other tasks
} Detection [x]Automatic [x] Automatic [x] You can detect this smell using static analysis tools or code reviews that check for unused variables after assignment. Most linters flag this as an issue. Tags Bloaters Bloaters Level [x]Beginner [x] Beginner [x] Why the Bijection Is Important It stays clean and efficient when your code accurately reflects real-world logic. real-world Unused assignments break this connection, making it harder to understand the intent and maintain the code. AI Generation AI tools seldom generate unused variable assignments when they misunderstand intent. AI Detection AI-assisted refactoring with clear instructions can flag unused variables and suggest removals, but it might not always understand if the return value should have been used. Try Them! Remember: AI Assistants make lots of mistakes Remember: AI Assistants make lots of mistakes Without Proper Instructions

With Specific Instructions



ChatGPT

ChatGPT



Claude

Claude



Perplexity

Perplexity



Copilot

Copilot



Gemini

Gemini



DeepSeek

DeepSeek



Meta AI

Meta AI Without Proper Instructions

With Specific Instructions ChatGPT

ChatGPT Claude

Claude Perplexity

Perplexity Copilot

Copilot Gemini

Gemini DeepSeek

DeepSeek Meta AI

Meta AI Without Proper Instructions With Specific Instructions Without Proper Instructions Without Proper Instructions With Specific Instructions With Specific Instructions ChatGPT ChatGPT ChatGPT ChatGPT ChatGPT ChatGPT ChatGPT ChatGPT Claude Claude Claude Claude Claude Claude Claude Claude Perplexity Perplexity Perplexity Perplexity Perplexity Perplexity Perplexity Perplexity Copilot Copilot Copilot Copilot Copilot Copilot Copilot Copilot Gemini Gemini Gemini Gemini Gemini Gemini Gemini Gemini DeepSeek DeepSeek DeepSeek DeepSeek DeepSeek DeepSeek DeepSeek DeepSeek Meta AI Meta AI Meta AI Meta AI Meta AI Meta AI Meta AI Meta AI Conclusion Unused variables after mutations create noise and confusion. mutations Don't assign the return value if you don't need it. If the method should return something meaningful, make sure you use it. Relations https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xlii?embedable=true https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xlii?embedable=true https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xxxvi?embedable=true https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xxxvi?embedable=true https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xxxi?embedable=true https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xxxi?embedable=true https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xxii?embedable=true https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-xxii?embedable=true More Information https://hackernoon.com/is-it-crystal-clear-for-everybody-that-a-date-should-not-mutate-wuoy3z03?embedable=true https://hackernoon.com/is-it-crystal-clear-for-everybody-that-a-date-should-not-mutate-wuoy3z03?embedable=true Disclaimer Code Smells are my opinion . opinion Credits Photo by Evan Demicoli on Unsplash Evan Demicoli Unsplash If you have to spend effort to decipher code, you should rewrite it. If you have to spend effort to decipher code, you should rewrite it. Martin Golding Martin Golding https://hackernoon.com/400-thought-provoking-software-engineering-quotes?embedable=true https://hackernoon.com/400-thought-provoking-software-engineering-quotes?embedable=true This article is part of the CodeSmell Series. https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-i-xqz3evd?embedable=true https://hackernoon.com/how-to-find-the-stinky-parts-of-your-code-part-i-xqz3evd?embedable=true

When You Forget to Throw, Your Code Will Blow 

Refactoring 022 - Extract Common Ancestor

Buy My Book

Share your ideas with me!

Read My Stories

Buy Me a Coffee

Too Long; Didn't Read

Make resilience your competitive advantage

Code Smell 287 - Unused Local Assignment

About Author

Comments

TOPICS

THIS ARTICLE WAS FEATURED IN

Related Stories

Untitled Story

Code Smell 309 - Query Parameter API Versioning

106 Stories To Learn About Clean Code

100 Pieces of Programming Advice from the Book Clean Code by Robert Martin

110 Stories To Learn About Refactoring

3 Things Coding And Prose Writing Have In Common According To Cory House

Code Smell 309 - Query Parameter API Versioning

106 Stories To Learn About Clean Code

100 Pieces of Programming Advice from the Book Clean Code by Robert Martin

110 Stories To Learn About Refactoring

3 Things Coding And Prose Writing Have In Common According To Cory House

Light-Mode

Classic

Newspaper

Dark-Mode

Neon Noir

Minty

HN StartUps