Sync vs Async JavaScript Explorer
What is Synchronous JavaScript?
Synchronous JavaScript runs code in order, one line at a time, waiting for each operation to complete before starting the next. So the program executes lines in sequence — X waits for Y to finish before starting Z.
// Example:
console.log("First");
console.log("Second");
console.log("Third");
// Output: First, Second, Third
What is Asynchronous JavaScript?
Asynchronous JavaScript lets long tasks (like timers or server requests) run in the background while the rest of the code continues. JavaScript uses an event loop to manage this. When an async task finishes, its callback runs later, after the current code is done.
// Example:
console.log("Hi");
setTimeout(() => console.log("Async!"), 1000);
console.log("End");
// Possible output:
// Hi
// End
// Async!
Why It Matters
- Synchronous code is simple and predictable but can block the browser if operations take time.
- Asynchronous code allows your app to stay responsive while waiting for slow tasks (like network calls).