Arrow functions are powerful — but they’re also tricky. Here are the common pitfalls (and fixes) every JavaScript beginner needs to know.

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Introduction: Why Beginners Struggle With Arrow Functions

Arrow functions look simple: drop the function keyword, add =>, done. But under the hood, they’re not just shorter syntax — they behave differently from regular functions in subtle ways.

That’s why beginners often misuse them. They forget about this, trip over implicit returns, or try to use them in places where they don’t belong.

In this guide, we’ll walk through 8 common mistakes beginners make with arrow functions — and how to fix them. By the end, you’ll not just use arrows, but understand when and why to use them.

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1. Forgetting Parentheses for Implicit Object Returns

The Mistake

// ❌ Wrong: JavaScript thinks {} is a function body
const makeUser = (id, name) => { id: id, name: name };

console.log(makeUser(1, "Ali")); 
// undefined

Why It Happens

Arrows allow implicit returns, but {} is interpreted as a block, not an object.

The Fix

Wrap the object in parentheses:

// ✅ Correct
const makeUser = (id, name) => ({ id, name });

console.log(makeUser(1, "Ali"));
// { id: 1, name: "Ali" }

💡 Rule: Always use () when implicitly returning objects.

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2. Using Arrow Functions as Methods

The Mistake

// ❌ Wrong
const user = {
  name: "Sara",
  greet: () => {
    return `Hi, I’m ${this.name}`;
  }
};

console.log(user.greet()); 
// "Hi, I'm undefined"

Why It Happens

Arrow functions don’t bind their own this. They inherit from the outer scope, which here is the global context — not the object.

The Fix

Use a regular function for object methods:

// ✅ Correct
const user = {
  name: "Sara",
  greet() {
    return `Hi, I’m ${this.name}`;
  }
};

console.log(user.greet()); 
// "Hi, I'm Sara"

💡 Rule: Don’t use arrow functions as methods if you need this.

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3. Using Arrow Functions as Constructors

The Mistake

// ❌ Wrong
const Person = (name) => {
  this.name = name;
};

const p = new Person("Ali"); 
// TypeError: Person is not a constructor

Why It Happens

Arrows don’t have their own this and can’t be used with new.

The Fix

Use a regular function or class for constructors:

// ✅ Correct
function Person(name) {
  this.name = name;
}

const p = new Person("Ali");
console.log(p.name); // "Ali"

💡 Rule: Never use arrow functions with new.

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4. Expecting arguments to Work

The Mistake

// ❌ Wrong
const sum = () => {
  return arguments[0] + arguments[1];
};

console.log(sum(2, 3)); 
// ReferenceError: arguments is not defined

Why It Happens

Arrow functions don’t have their own arguments object.

The Fix

Use rest parameters:

// ✅ Correct
const sum = (...args) => args[0] + args[1];

console.log(sum(2, 3)); 
// 5

💡 Rule: Use ...args with arrows instead of arguments.

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5. Overusing Implicit Returns

The Mistake

// ❌ Hard to read
const isValid = val => val !== null && val !== undefined && val !== "";

Why It Happens

Implicit returns are nice, but cramming too much into one line kills readability.

The Fix

Use braces + return when logic grows:

// ✅ Clearer
const isValid = val => {
  return val !== null && val !== undefined && val !== "";
};

💡 Rule: Implicit returns are for simple expressions, not complex logic.

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6. Forgetting About Line Breaks

The Mistake

// ❌ Wrong
const add = (a, b) => 
a + b;

console.log(add(2, 3)); 
// undefined

Why It Happens

When you put a line break after =>, JavaScript inserts an implicit ; before the expression.

The Fix

Put the expression on the same line, or wrap in parentheses:

// ✅ Correct
const add = (a, b) => a + b;

// ✅ Or
const addMultiLine = (a, b) => (
  a + b
);

console.log(add(2, 3)); // 5

💡 Rule: Be careful with line breaks after =>.

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7. Misusing this in Event Handlers

The Mistake

// ❌ Wrong
const button = document.querySelector("button");
button.addEventListener("click", () => {
  console.log(this); // Window, not button
});

Why It Happens

Arrow functions inherit this from their parent scope, not the element.

The Fix

Use a regular function when you want this bound to the element:

// ✅ Correct
button.addEventListener("click", function () {
  console.log(this); // The button element
});

💡 Rule: Use arrows for callbacks when you don’t need dynamic this.

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8. Thinking Arrow Functions Are Always Better

The Mistake

Beginners sometimes replace all functions with arrows, even when not appropriate.

// ❌ Wrong: Using arrow everywhere
const obj = {
  count: 0,
  increment: () => this.count++
};

Why It Happens

They assume arrows are a strict upgrade.

The Fix

Choose the right tool for the job:

• Use regular functions for methods, constructors, and dynamic this.
• Use arrows for callbacks, utilities, and functional programming.

// ✅ Balanced use
const obj = {
  count: 0,
  increment() { this.count++; }
};

setTimeout(() => obj.increment(), 100);

💡 Rule: Arrows are powerful, but not universal.

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Wrapping It All Up

Here are the 8 mistakes beginners make with arrow functions (and fixes):

1. Forgetting parentheses for implicit object returns → wrap in ().
2. Using arrows as methods → use regular functions if you need this.
3. Using arrows as constructors → not possible.
4. Expecting arguments to work → use rest parameters.
5. Overusing implicit returns → keep them simple.
6. Breaking lines after => → use same line or parentheses.
7. Misusing this in event handlers → use regular functions.
8. Thinking arrows are always better → choose wisely.

Arrow functions are amazing — but only when you understand their rules. Learn these, and you’ll avoid subtle bugs that trip up beginners everywhere.

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Call to Action

👉 Which of these mistakes have you made before? Drop it in the comments 👇.

📤 Share this with a beginner dev in your team.
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