Sequential vs parallel execution in Javascript - Quick Revision & Key Differences

Recall & Review

beginner

What is sequential execution in JavaScript?

Sequential execution means running code one step at a time, in order. Each step waits for the previous one to finish before starting.

beginner

What does parallel execution mean?

Parallel execution means running multiple tasks at the same time, so they can finish faster by working together.

intermediate

How does JavaScript handle parallel execution since it has a single thread?

JavaScript uses asynchronous features like promises and async/await to start tasks that run in the background, allowing other code to run without waiting.

intermediate

What is the role of Promise.all() in parallel execution?

Promise.all() lets you run multiple promises at the same time and wait for all of them to finish before continuing.

intermediate

Give an example of sequential vs parallel execution using async functions.

Sequential: await task1(); await task2(); runs task2 after task1 finishes.<br>Parallel: await Promise.all([task1(), task2()]); runs both tasks at the same time.

Which of these best describes sequential execution?

A Tasks run randomly

B Tasks run all at the same time

C Tasks run one after another, waiting for each to finish

D Tasks never finish

Sequential execution means tasks run one by one, each waiting for the previous to finish.

What JavaScript feature helps run tasks in parallel?

A Console.log

B For loops

C Variables

D Promises and async/await

Promises and async/await allow JavaScript to handle tasks asynchronously, enabling parallel execution.

What does Promise.all() do?

A Runs multiple promises in parallel and waits for all to finish

B Runs promises one by one

C Cancels all promises

D Creates a new promise that never resolves

Promise.all() runs promises together and waits until all complete.

If you write await task1(); await task2();, how do tasks run?

A In parallel, both start together

B Sequentially, task2 waits for task1

C Only task2 runs

D Both tasks are skipped

Using await one after another runs tasks sequentially.

Why is parallel execution useful?

A It can make programs faster by doing many things at once

B It makes code harder to read

C It always uses more memory

D It stops programs from running

Parallel execution helps programs finish tasks faster by running them simultaneously.

Explain the difference between sequential and parallel execution in JavaScript.

Think about waiting for tasks to finish or running them together.

How does Promise.all() help with parallel execution?

It collects many promises and waits for all.