Regular iterators work for synchronous data.

But what about:
        - API responses
        - File streams
        - WebSockets
- Large data pipelines

That’s where Async Iterators shine.

## 🔹 What Is an Async Iterator?

An async iterator returns a Promise from `next()`.

Instead of:

```js
iterator.next();

You get:

await iterator.next();

🔹 Async Generator Basics

async function* fetchData() {
yield await fetch("/api/1").then(r => r.json());
yield await fetch("/api/2").then(r => r.json());
}

Notice the async function*.

🔹 Using for await…of

for await (const data of fetchData()) {
console.log(data);
}

This automatically waits for each Promise.

🔹 Why Not Just Use Promise.all?

Promise.all waits for everything at once.

Async Iterators:
    •    Process data progressively
    •    Reduce memory usage
    •    Improve responsiveness

🔹 Example: Simulated Streaming

async function* delayed() {
let i = 0;
while (i < 3) {
await new Promise(r => setTimeout(r, 1000));
yield i++;
}
}

Values arrive gradually.

🔹 Async Iterator Protocol

An object is async iterable if it implements:

Symbol.asyncIterator

Example:

const obj = {
async *[Symbol.asyncIterator]() {
yield 1;
yield 2;
}
};

🔹 Sync vs Async Iterators

🔹 Real-World Use Cases
    •    Fetch streaming APIs
    •    Node.js streams
    •    Pagination handling
    •    Event processing
    •    Real-time dashboards

🔹 When to Use Async Iterators

Use when:
    •    Data arrives over time
    •    You need progressive processing
    •    Memory efficiency matters

Avoid when:
    •    All data is already available
    •    Simple async/await is enough

🎯 Final Thought

Sync iterators walk through data.
Async iterators wait for it.

Async Iterators let JavaScript handle streaming data elegantly.