gaearon

Note:

When this guide is more complete, the plan is to move it into Prepack documentation.
For now I put it out as a gist to gather initial feedback.

A Gentle Introduction to Prepack (Part 1)

If you're building JavaScript apps, you might already be familiar with some tools that compile JavaScript code to equivalent JavaScript code:

• Babel lets you use newer JavaScript language features, and outputs equivalent code that targets older JavaScript engines.

Rich-Harris

Edit — February 2019

This gist had a far larger impact than I imagined it would, and apparently people are still finding it, so a quick update:

• TC39 is currently moving forward with a slightly different version of TLA, referred to as 'variant B', in which a module with TLA doesn't block sibling execution. This vastly reduces the danger of parallelizable work happening in serial and thereby delaying startup, which was the concern that motivated me to write this gist
• In the wild, we're seeing (async main(){...}()) as a substitute for TLA. This completely eliminates the blocking problem (yay!) but it's less powerful, and harder to statically analyse (boo). In other words the lack of TLA is causing real problems
• Therefore, a version of TLA that solves the original issue is a valuable addition to the language, and I'm in full support of the current proposal, which you can read here.

I'll leave the rest of this document unedited, for archaeological

rauschma

Cheat sheet for callable entities in ES6

Value:

	FD	FE	AF	C	M
Function-callable	✓	✓	✓	×	✓
Constructor-callable	✓	✓	×	✓	×
Prototype	F.p	F.p	F.p	SC	F.p
Property prototype	✓	✓	×	✓	×

paulirish

What forces layout / reflow

All of the below properties or methods, when requested/called in JavaScript, will trigger the browser to synchronously calculate the style and layout*. This is also called reflow or layout thrashing, and is common performance bottleneck.

Generally, all APIs that synchronously provide layout metrics will trigger forced reflow / layout. Read on for additional cases and details.

Element APIs

Getting box metrics

• elem.offsetLeft, elem.offsetTop, elem.offsetWidth, elem.offsetHeight, elem.offsetParent

CMCDragonkai

HTTP Streaming (or Chunked vs Store & Forward)

The standard way of understanding the HTTP protocol is via the request reply pattern. Each HTTP transaction consists of a finitely bounded HTTP request and a finitely bounded HTTP response.

However it's also possible for both parts of an HTTP 1.1 transaction to stream their possibly infinitely bounded data. The advantages is that the sender can send data that is beyond the sender's memory limit, and the receiver can act on

jhorneman

Async data loading in Flux

I've been working with Flux a lot recently, and one of the questions I've been struggling with is in which part of the Flux cycle to put my asynchronous data requests.

Here are some different opinions:

The diagram

The famous Flux diagram puts them in the action creators.

The chat example

larahogan

Native app performance metrics

This is a draft list of what we're thinking about measuring in Etsy's native apps.

Currently we're looking at how to measure these things with Espresso and Kif (or if each metric is even possible to measure in an automated way). We'd like to build internal dashboards and alerts around regressions in these metrics using automated tests. In the future, we'll want to measure most of these things with RUM too.

Overall app metrics

• App launch time - how long does it take between tapping the icon and being able to interact with the app?
• Time to complete critical flows - using automated testing, how long does it take a user to finish the checkout flow, etc.?
• Battery usage, including radio usage and GPS usage
• Peak memory allocation

wincent

2015-01-29 Unofficial Relay FAQ

Compilation of questions and answers about Relay from React.js Conf.

Disclaimer: I work on Relay at Facebook. Relay is a complex system on which we're iterating aggressively. I'll do my best here to provide accurate, useful answers, but the details are subject to change. I may also be wrong. Feedback and additional questions are welcome.

What is Relay?

Relay is a new framework from Facebook that provides data-fetching functionality for React applications. It was announced at React.js Conf (January 2015).

nikcorg

Jake Archibald (@jaffathecake): The ServiceWorker is coming; look busy
https://speakerdeck.com/jaffathecake/the-serviceworker-is-coming-look-busy https://github.com/jakearchibald/trained-to-thrill/
https://www.youtube.com/watch?v=SmZ9XcTpMS4

Hunter Loftis (@hunterloftis): We Will All Be Game Progmrammers
http://wwabgp.herokuapp.com/s
http://youtu.be/QX0eauXBKwc

CarterRabasa (@carterrabasa): A Community of People; Not Projects

staltz

The introduction to Reactive Programming you've been missing

(by @andrestaltz)

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This tutorial as a series of videos

If you prefer to watch video tutorials with live-coding, then check out this series I recorded with the same contents as in this article: Egghead.io - Introduction to Reactive Programming.

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