Asynchronous in JavaScript

Source: Dev.to

🔴 Synchronous (Normal)

One task mudinja apram thaan next task start aagum.

console.log("One");
console.log("Two");
console.log("Three");

👉 Output

One
Two
Three

🟢 Asynchronous

Long task background‑la nadakkum, short task immediate‑aa execute aagum.

console.log("Start");

setTimeout(() => {
  console.log("Middle");
}, 2000);

console.log("End");

👉 Output

Start
End
Middle

🔹 Why Asynchronous needed?

• API call time edukkum
• File loading time edukkum
• Timer, user input wait

👉 App freeze aagama irukka asynchronous use pannrom.

🔹 Common Asynchronous methods

1️⃣ setTimeout()

Delay ku apram run aagum.

setTimeout(() => {
  console.log("Hello");
}, 1000);

2️⃣ setInterval()

Repeated‑aa run aagum.

setInterval(() => {
  console.log("Hi");
}, 2000);

3️⃣ Promise

Future‑la result varum nu promise.

let promise = new Promise((resolve, reject) => {
  resolve("Success");
});

4️⃣ async / await

Promise‑a simple‑aa handle panna.

async function loadData() {
  let result = await fetch(url);
}