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Cover image for Code Smell 247 - Javascript Replace
Maxi Contieri
Maxi Contieri

Posted on • Originally published at

Code Smell 247 - Javascript Replace

You want to replace all, but you replace one ocurrence

TL;DR: Bad function names will lead you to defects



  1. Avoid ambiguous or bad names

  2. Wrap with your functions

  3. Use mature languajes


Some names in immature languages break the bijection principle.

When you use them, you agree on some semantics that are not the actual behavior.

Consequently, you must know accidental implementations to avoid this defect.

Sample Code


const pets = '😺🐶😺';
const justDogs = pets.replace('😺', '🐩');

const catsArePresent = justDogs.includes('😺');
// returns true
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const pets = '😺🐶😺';

const justDogs = pets.replaceAll('😺', '🐩');
// Or
const justDogs = pets.replace(/😺/g, '');

const catsArePresent = justDogs.includes('😺');
// returns false
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[X] Automatic

You can search and forbid the usage of replace() in your code and define replaceFirst() if you need to change only the first occurrence


  • Naming


[x] Beginner

AI Generation

All generators avoided this problem.

AI Detection

ChatGPT and Copilot use Regular Expressions to solve the problem.

Gemini and Claude failed to spot the mistake.

None of them use replaceAll() (introduced in ES2021)


Using replace() instead of replaceAll() would not fully achieve the intended result of replacing all occurrences.

It would only replace the first occurrence, potentially leading to incorrect behavior if there are multiple occurrences.


More Info


Code Smells are my opinion.


Photo by Jari Hytönen on Unsplash

We must not blame programmers for their bugs. They belong to them only until the code is merged to the repository. After that, all bugs are ours!

Yegor Bugayenko

This article is part of the CodeSmell Series.

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