JavaScript Best Practices

Writing code that works is good—but writing code that is clean, efficient, and easy to maintain is even better. JavaScript is flexible, but that flexibility can lead to messy or error-prone code if not handled properly. That’s why it’s important to follow best practices that help you write professional-quality JavaScript.

This tutorial covers essential JavaScript best practices you should adopt for clean, readable, and bug-free code.

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1. Use let and const, Never var

var is function-scoped and can cause unexpected behavior due to hoisting. Instead, use:

• const for values that don’t change.
• let for values that will change.

javascriptCopyEditconst maxUsers = 100;
let currentUsers = 5;

Avoid:

javascriptCopyEditvar currentUsers = 5; // old and unsafe

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2. Write Descriptive Variable and Function Names

Good naming makes your code more readable and self-documenting.

javascriptCopyEdit// Good
let userCount = 10;
function calculateDiscount(price) {
  return price * 0.1;
}

// Bad
let x = 10;
function cd(p) {
  return p * 0.1;
}

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3. Keep Functions Small and Focused

A function should do one thing only. If a function is too long or does multiple things, break it into smaller functions.

javascriptCopyEdit// Good
function getUserInfo() {
  fetchUser();
  displayUser();
}

// Bad
function handleEverything() {
  fetchUser();
  displayUser();
  logUserActivity();
  sendAnalytics();
}

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4. Use Strict Equality (=== and !==)

Avoid == and !=, which allow type coercion that can lead to unexpected results.

javascriptCopyEdit// Good
if (score === 100) {
  console.log("Perfect score!");
}

// Bad
if (score == "100") {
  console.log("Perfect score?");
}

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5. Avoid Global Variables

Variables in the global scope can be overwritten easily, leading to hard-to-find bugs. Wrap your code in functions or modules.

javascriptCopyEdit// Good
function initApp() {
  const config = {};
}

// Bad
const config = {}; // Global variable

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6. Handle Errors with try...catch

Always catch exceptions where failures might happen, like JSON parsing or API calls.

javascriptCopyEdittry {
  const data = JSON.parse(response);
} catch (error) {
  console.error("Invalid JSON:", error.message);
}

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7. Don’t Repeat Yourself (DRY Principle)

Avoid copying and pasting code. If you’re writing the same logic in multiple places, turn it into a function.

javascriptCopyEdit// Good
function greet(name) {
  return `Hello, ${name}!`;
}

greet("Alice");
greet("Bob");

// Bad
console.log("Hello, Alice!");
console.log("Hello, Bob!");

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8. Use Arrow Functions for Simple Callbacks

Arrow functions are shorter and cleaner, especially for callbacks.

javascriptCopyEdit// Good
const numbers = [1, 2, 3];
const doubled = numbers.map(n => n * 2);

// Bad
const doubled = numbers.map(function(n) {
  return n * 2;
});

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9. Avoid Magic Numbers and Strings

Use named constants instead of hard-coded values.

javascriptCopyEdit// Good
const MAX_USERS = 100;
if (users.length > MAX_USERS) {
  alert("Too many users");
}

// Bad
if (users.length > 100) {
  alert("Too many users");
}

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10. Comment Wisely and Only When Needed

Comments should explain why something is done, not what—the code should already be clear about what it’s doing.

javascriptCopyEdit// Good
// Convert minutes to seconds
function toSeconds(minutes) {
  return minutes * 60;
}

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Bonus: Use Tools to Enforce Best Practices

• ESLint – Checks for bad practices and common bugs.
• Prettier – Automatically formats your code.
• TypeScript – Adds optional typing to JavaScript for better tooling and safety.

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Conclusion

Following JavaScript best practices makes your code more reliable, readable, and maintainable—skills that are crucial in both personal and professional projects.

To recap:

• Use let and const, not var.
• Name your variables and functions clearly.
• Write small, focused functions.
• Use strict equality and error handling.
• Avoid code duplication and global variables.
• Use tools like ESLint and Prettier to keep your code clean.