Why Arrow Functions Were Introduced

Arrow functions were not introduced to replace regular functions — they were added to solve specific problems that arose with this and function expressions in functional-style programming and callbacks.

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🔑 Key Reasons for Arrow Functions

1. ✅ Lexical this binding

In many cases, especially with event handlers, callbacks, or setTimeout, regular functions caused problems with this.

🧱 Problem with this in regular functions:

function Timer() {
  this.seconds = 0;
  setInterval(function () {
    this.seconds++;
    console.log(this.seconds); // ❌ NaN or undefined
  }, 1000);
}

• Here, this inside setInterval refers to the window object, not the Timer instance.

✅ Arrow functions fix this:

function Timer() {
  this.seconds = 0;
  setInterval(() => {
    this.seconds++;
    console.log(this.seconds); // ✅ Works as expected
  }, 1000);
}

• Arrow functions capture this from the surrounding context (lexical scoping), solving a long-standing headache.

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2. ✅ Shorter syntax for inline functions

Functional programming patterns use a lot of small functions like:

const doubled = arr.map(function(n) {
  return n * 2;
});

With arrow functions:

const doubled = arr.map(n => n * 2);

It’s more concise, especially for one-liners.

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3. ✅ Better for callbacks / promises

In chaining or async code, they reduce clutter:

fetch('/api')
  .then(res => res.json())
  .then(data => console.log(data));

This would be unnecessarily verbose with traditional functions.

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🚫 The Downsides

Arrow functions:

• ❌ Can make this confusing when used inside objects.

• ❌ Reduce readability for beginners.

• ❌ Are not suitable for object methods.

• ❌ Have no arguments object, which sometimes matters.

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🧠 Summary

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💬 Final Thought

Arrow functions should not be used blindly.
Use them:

• For callbacks, short functions, and functional programming patterns.

• Avoid them for object methods where you rely on this.

In short: arrow functions are a tool, not a replacement.