Sequential vs parallel execution in Javascript - When to Use Which

The Big Idea

What if your program could do many things at once instead of waiting forever?

The Scenario

Imagine you have to bake 5 cakes one after another, waiting for each to finish before starting the next.

It takes a long time, and you get bored waiting.

The Problem

Doing tasks one by one means you waste time waiting for each to finish.

If one task is slow, everything else waits too.

This makes your program slow and less efficient.

The Solution

Parallel execution lets you start many tasks at the same time.

Like baking all cakes in different ovens together, saving lots of time.

JavaScript can run tasks in parallel using promises and async functions.

Before vs After

✗ Before

await bakeCake(1);
await bakeCake(2);
await bakeCake(3);

✓ After

await Promise.all([bakeCake(1), bakeCake(2), bakeCake(3)]);

What It Enables

You can do many things at once, making your programs faster and more responsive.

Real Life Example

Loading images on a webpage one by one makes users wait longer.

Loading them in parallel shows all images faster, improving user experience.

Key Takeaways

Sequential execution runs tasks one after another, which can be slow.

Parallel execution runs tasks at the same time, saving time.

JavaScript uses promises and async/await to handle parallel tasks easily.