Hasty Treat - JavaScript Event Buzzwords — Sync, Concurrent, Defer, Blocking, Workers

Jul 5, 2021

Discover the fascinating world of JavaScript buzzwords, including the differences between synchronous and asynchronous operations. Understand how multi-threading with web workers enhances performance. Dive into the concepts of blocking, concurrency, and parallelism, and how these impact your coding. Learn about optimizing script loading with async and defer attributes for a smoother user experience. Plus, explore the benefits of lazy loading in web development to boost website performance.

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INSIGHT

Synchronous vs. Asynchronous

Synchronous tasks are done one after another, blocking the next task until completion.
Asynchronous tasks can start and continue independently, allowing multiple tasks to happen concurrently.

INSIGHT

Multi-threading and JavaScript

Threads relate to CPU processing, allowing concurrent or parallel execution of tasks.
JavaScript is single-threaded, but web workers enable background multi-threading.

INSIGHT

Blocking Operations

Blocking operations halt other processes, impacting responsiveness.
Script tags can block rendering, while Node.js file operations can block the server.

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In this Hasty Treat, Scott and Wes define some JavaScript Buzzwords and talk about what they mean!

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Show Notes

03:24 - Synchronous / Async

05:23 - Multi-threaded

JavaScript has a single “main thread”
But you can have more threads with web workers

08:12 - Blocking

JavaScript can stop other things on the page from running
A script tag can block HTML from being parsed
Most stuff in JavaScript is non-blocking
Node.js write to filesystem can be blocking

10:27 - Concurrent + Parallel

JavaScript start/stop are concurrent
The API runs on a different thread
Doesn’t REALLY matter
https://joearms.github.io/published/2013-04-05-concurrent-and-parallel-programming.html

13:22 - Consecutive / Waterfall

One after another

13:48 - Callback

A function to run when this thing happens or is done
Click event callback
Websocket on data callback
- Like a tweet stream
Data fetch callback
- Almost entirely replaced with async + await
http://callbackhell.com/
https://caolan.github.io/async/v3/

17:56 - Script Tag Async + Defer

Doesn’t block other content
Runs when ready - doesn’t care about DOMcontentLoaded
Wait until the page is loaded before running
If the script tag is above content, don’t wait for it
Good for things that aren’t called on page load

21:54 - Lazy

Load it in later - maybe when it’s scrolled into view, or as needed
Not mission-critical

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