🧠 11 Rules to Instantly Improve Your Code Quality (with JavaScript Examples)

Code that works is good. Code that’s clear, simple, and maintainable? That’s great.

Here are 11 battle-tested rules—with JavaScript examples—to help you write better code that your future self (and teammates) will thank you for:

1. Keep it Simple

💡 Bad:

const result = !!(a && b && !(c || d));        

✅ Better:

const hasInput = a && b; 
const isInvalidState = c || d; 
const result = hasInput && !isInvalidState;        

Clarity > cleverness.

2. Use Clear, Descriptive Names

💡 Bad:

function calc(x, y) { 
       return x * y * 0.9; 
}        

✅ Better:

function calculateDiscountedPrice(price, quantity) { 
       return price * quantity * 0.9; 
}        

Descriptive naming makes comments almost unnecessary.

3. Limit Dependencies (Avoid Deep Chaining)

💡 Bad:

const creditScore = order.customer.account.credit.score;        

✅ Better:

const { customer } = order; 
const creditScore = customer.creditScore;        

Too much chaining = fragile, tightly coupled code.

4. Avoid Overusing if Statements

💡 Bad:

if (fileType === 'pdf') { 
   exportPdf(data); 
} else if (fileType === 'csv') {
   exportCsv(data); 
} else if (fileType === 'json') { 
   exportJson(data); 
}        

✅ Better:

const exporters = { 
pdf: exportPdf, 
csv: exportCsv, 
json: exportJson, 
}; 
exporters[fileType]?.(data);        

Simplify logic using objects and maps.

5. One Job per Function

💡 Bad:

function handleUserSignup(user) {
  // Validate input
  if (!user.email.includes('@')) {
    throw new Error('Invalid email');
  }

  // Save to database
  database.save(user);

  // Send welcome email
  emailService.send({
    to: user.email,
    subject: 'Welcome!',
    body: 'Thanks for signing up!',
  });
}        

🔴 This function is:

• Validating input
• Saving data
• Sending email

That’s three separate responsibilities. It violates the Single Responsibility Principle.

✅ Better:

function validateUser(user) {
  if (!user.email.includes('@')) {
    throw new Error('Invalid email');
  }
}

function saveUser(user) {
  database.save(user);
}

function sendWelcomeEmail(user) {
  emailService.send({
    to: user.email,
    subject: 'Welcome!',
    body: 'Thanks for signing up!',
  });
}

function handleUserSignup(user) {
  validateUser(user);
  saveUser(user);
  sendWelcomeEmail(user);
}
        

🟢 Now each function:

• Has a single purpose
• Is easier to test and reuse
• Makes handleUserSignup() a clear orchestrator, not a bloated block of logic

6. Often ‘over-engineering’ is proper engineering

Believe me, I get the notion of over-engineering. I just told you to keep things simple. But sometimes, doing things “the right way” looks like over-engineering. Whenever you think you are over-engineering, stop and consider that, well, maybe you aren’t. Creating interfaces and coding against them can seem like over-engineering. I know it’s a fine line to walk, but planning ahead for something you know you will need is not wrong. And this leads me to…

7. Use Explaining Variables

💡 Bad:

if (user.age > 18 && user.isVerified && user.subscription) { allowAccess(); 
}        

✅ Better:

const isEligible = user.age > 18 && user.isVerified && user.subscription; if (isEligible) { 
   allowAccess(); 
}        

Naming makes conditions easier to understand at a glance.

8. No Magic Numbers

💡 Bad:

if (items.length > 42) return true;         

✅ Better:

const MAX_ITEMS = 42; 
if (items.length > MAX_ITEMS) return true;         

Constants make your code more flexible and expressive.

9. Make the command line your first user interface

All of your business logic and other, non-interface code should be accessible via a command-line application. If you can’t run your code at the command line, and it requires some kind of GUI or other interface to run, then you have improperly coupled your code and possibly tied it in knots.

This is an approach that I started taking when I realized that at the heart of all crappy code is the tying of business logic to the user interface. The two should be treated like oil and vinegar, but all too often they are mixed together like Kool-Aid. Separate your concerns and prove it by running your code with a command-line application.

10. Refactor Without Fear

💡 Bad:

function userInfo(user) {
 return ${user.firstName} ${user.lastName} - ${user.role} -    ${user.department}; 
}        

✅ Better:

function formatUserName(user) { 
 return ${user.firstName} ${user.lastName}; 
} 
function formatUserDetails(user) { 
 return ${user.role} - ${user.department}; 
} 
function userInfo(user) {
 return ${formatUserName(user)} - ${formatUserDetails(user)}; 
}        

Small refactors lead to cleaner, more testable code.

11. Code for the Next Developer

💡 Don’t write code only you can understand. Someone else will read and maintain it—possibly you, six months from now. Clear structure, meaningful names, and small functions go a long way.

✅ Final Thought

Clean code isn’t about writing more code—it’s about writing better, more intentional code.

You don’t need to follow all 11 rules at once. Start with 2 or 3. Refactor often. Get feedback. Iterate.

👀 Which of these do you follow? Which one do you still struggle with?

Let’s grow together—drop your thoughts below 👇

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