Every developer starts somewhere, and we’ve all written questionable code at some point.

But some habits can silently sabotage your projects — slowing performance, increasing bugs, and making life hard for your future self (or your team).

If you want to write cleaner, faster, and more maintainable JavaScript, it's time to stop using these common anti-patterns.

Let's fix them together.

1. Global Variables Everywhere

Defining too many global variables can lead to namespace pollution and unexpected bugs — especially in large or team projects.

❌ Don’t do this:

let user = "admin";
function login() {
  console.log("Logged in:", user);
}

✅ Do this instead:

(function() {
  let user = "admin";
  function login() {
    console.log("Logged in:", user);
  }
  login();
})();

📚 Learn more about [JavaScript Scope and Closures](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Closures)

2. Abusing == Instead of ===

Loose equality can be... very loose.

console.log("0" == 0); // true 😬
console.log(false == ""); // true 😬

Always use === unless you absolutely know what you're doing.

✅ Prefer:

if (userId === "123") {
  // safe check
}

Great breakdown on this topic: [JavaScript Equality Table](https://dorey.github.io/JavaScript-Equality-Table/)

3. Modifying Built-In Prototypes

Sure, it sounds cool to extend native objects... until you break libraries or cause compatibility issues.

❌ Don’t:

Array.prototype.first = function() {
  return this[0];
}

✅ Create utility functions instead:

function getFirst(arr) {
  return arr[0];
}

Still curious? [Why extending prototypes is dangerous](https://stackoverflow.com/questions/14034180/why-is-extending-native-objects-a-bad-practice)

4. Callback Hell

Nested callbacks make your code hard to read and even harder to debug.

doSomething(function(err, result) {
  doSomethingElse(result, function(err2, result2) {
    // and so on...
  });
});

✅ Use async/await:

async function run() {
  const result = await doSomething();
  const result2 = await doSomethingElse(result);
}

Want to master async/await? [JavaScript.info Async Programming](https://javascript.info/async)

5. Declaring Variables Without let, const, or var

Forgetting to declare variables makes them global unintentionally.

❌ Avoid:

function greet() {
  name = "Alex"; // becomes global
}

✅ Fix:

function greet() {
  const name = "Alex";
}

It’s a small thing that leads to big bugs.

6. Too Many Comments (Or None At All)

Over-commenting every single line or not commenting at all are both extremes. Instead:

✅ Write self-explanatory code and comment why, not what.

// Avoid resetting if already initialized
if (!config.initialized) {
  initializeConfig();
}

📘 Read: Clean Code JavaScript

7. Copy-Pasting Stack Overflow Code Without Understanding

We've all been there. But code you don’t understand can introduce subtle bugs and security issues.

✅ Always read and test before using it. Even better — learn why it works.

Start learning from scratch here:

🧠 JavaScript Roadmap for Beginners

📹 JavaScript Tutorials by The Net Ninja

💬 Which of these anti-patterns have you seen (or done 😅)? Drop your confessions in the comments!

🧠 Share this with a fellow dev who needs a reminder.

📌 Save this post so you never forget these common traps.

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