JavaScript is flexible.
Sometimes too flexible.
At first, that flexibility feels like freedom. You can write code fast, ship features, and move on. But months later—when you or someone else has to touch the same file again—things suddenly feel painful.
I’ve been there. Opening a file I wrote myself and thinking, “Who wrote this mess?”
Spoiler: it was me.
Here are ten JavaScript habits that don’t break your app immediately—but quietly sabotage maintainability over time.
1. Overusing Anonymous Functions Everywhere
Anonymous functions are convenient. They’re also invisible in stack traces.
When something breaks, debugging becomes harder because errors point to (anonymous) instead of something meaningful.
Better approach:
Name functions that do real work. Your future self will thank you.
2. Mixing Business Logic With UI Logic
When API calls, validation, and DOM manipulation live in the same function, changes become risky.
You fix one thing, three others break.
Better approach:
Separate concerns. Keep logic independent from presentation whenever possible.
3. Relying on “Magic” Values
Hardcoded strings, numbers, or flags scattered across files create invisible dependencies.
Change one value? Good luck finding all the places it’s used.
Better approach:
Use constants. Centralize shared values.
4. Writing Functions That Do Too Much
If a function needs comments to explain what it does, it’s probably doing more than one thing.
Long functions hide bugs well.
Better approach:
Small, focused functions with clear responsibility.
5. Ignoring Error Handling Because “It Works”
Happy-path-only code is fragile.
APIs fail. Inputs break. Browsers behave differently.
Better approach:
Handle errors intentionally. Even basic try/catch blocks improve resilience.
6. Inconsistent Naming Conventions
Mixing camelCase, snake_case, and vague names like data or temp creates mental overhead.
Your brain spends more time decoding than solving problems.
Better approach:
Pick a convention. Stick to it religiously.
7. Mutating Objects You Don’t Own
Mutating shared objects creates side effects that are hard to trace.
The bug shows up far away from where it started.
Better approach:
Favor immutability. Create copies when modifying data.
8. Commenting What Instead of Why
Comments that restate the code add noise.
The real value lies in explaining why something exists—not what it does.
Better approach:
Let code explain the “what.” Use comments for decisions and context.
9. Skipping Formatting Because “The Linter Will Handle It”
Linters help, but unreadable structure still hurts comprehension.
Better approach:
Write clean code first. Let tools reinforce—not replace—clarity.
10. Not Deleting Old Code
Dead code accumulates like dust.
Soon nobody knows what’s safe to remove.
Better approach:
Delete unused code. Version control exists for a reason.
Closing Thought
Maintainable JavaScript isn’t about being clever.
It’s about being clear, boring, and predictable.
Your code doesn’t just need to run today—it needs to be understandable six months from now.