Andrei Xavier de Oliveira Calazans AndreiCalazans

Array Iteration

https://gist.github.com/ljharb/58faf1cfcb4e6808f74aae4ef7944cff

While attempting to explain JavaScript's reduce method on arrays, conceptually, I came up with the following - hopefully it's helpful; happy to tweak it if anyone has suggestions.

Intro

JavaScript Arrays have lots of built in methods on their prototype. Some of them mutate - ie, they change the underlying array in-place. Luckily, most of them do not - they instead return an entirely distinct array. Since arrays are conceptually a contiguous list of items, it helps code clarity and maintainability a lot to be able to operate on them in a "functional" way. (I'll also insist on referring to an array as a "list" - although in some languages, List is a native data type, in JS and this post, I'm referring to the concept. Everywhere I use the word "list" you can assume I'm talking about a JS Array) This means, to perform a single operation on the list as a whole ("atomically"), and to return a new list - thus making it mu

FWIW: I (@rondy) am not the creator of the content shared here, which is an excerpt from Edmond Lau's book. I simply copied and pasted it from another location and saved it as a personal note, before it gained popularity on news.ycombinator.com. Unfortunately, I cannot recall the exact origin of the original source, nor was I able to find the author's name, so I am can't provide the appropriate credits.

Effective Engineer - Notes

By Edmond Lau
Highly Recommended 👍
http://www.theeffectiveengineer.com/

What's an Effective Engineer?

Stuff I wish I'd known sooner about service workers

I recently had several days of extremely frustrating experiences with service workers. Here are a few things I've since learned which would have made my life much easier but which isn't particularly obvious from most of the blog posts and videos I've seen.

I'll add to this list over time – suggested additions welcome in the comments or via twitter.com/rich_harris.

Use Canary for development instead of Chrome stable

~~Chrome 51 has some pretty wild behaviour related to console.log in service workers. Canary doesn't, and it has a load of really good service worker related stuff in devtools.~~

In the below keyboard shortcuts, I use the capital letters for reading clarity but this does not imply shift, if shift is needed, I will say shift. So ⌘ + D does not mean hold shift. ⌘ + Shift + D does of course.

Tabs and Windows

Function	Shortcut
New Tab	`⌘` + `T`
Close Tab or Window	`⌘` + `W` (same as many mac apps)
Go to Tab	`⌘` + `Number Key` (ie: `⌘2` is 2nd tab)
Go to Split Pane by Direction	`⌘` + `Option` + `Arrow Key`

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

Some thoughts on using node-postgres in a web application

This is the approach I've been using for the past year or so. I'm sure I'll change and it will change as I grow & am exposed to more ideas, but it's worked alright for me so far.

Pooling:

I would definitely use a single pool of clients throughout the application. node-postgres ships with a pool implementation that has always met my needs, but it's also fine to just use the require('pg').Client prototype and implement your own pool if you know what you're doing & have some custom requirements on the pool.

	import Exponent from 'exponent';
	import React from 'react';
	import { range } from 'lodash';

	import {
	StyleSheet,
	Dimensions,
	ScrollView,
	Animated,
	Text,

	Zig 0.371 sec
	C 0.604 sec


	implementations of the RNG are equivalent implementations of MT64

	note: I achieved the same performance with zig and C when I used clang with -O3 -fomit-frame-pointer and LTO.

	RN < 0.50 - watchman watch-del-all && rm -rf $TMPDIR/react-* && rm -rf node_modules/ && npm cache clean && npm install && npm start -- --reset-cache
	RN >= 0.50 - watchman watch-del-all && rm -rf $TMPDIR/react-native-packager-cache-* && rm -rf $TMPDIR/metro-bundler-cache-* && rm -rf node_modules/ && npm cache clean && npm install && npm start -- --reset-cache
	RN >= 0.63 - watchman watch-del-all && rm -rf node_modules && npm install && rm -rf /tmp/metro-* && npm run start --reset-cache

	npm >= 5 - watchman watch-del-all && rm -rf $TMPDIR/react-* && rm -rf node_modules/ && npm cache verify && npm install && npm start -- --reset-cache

	Windows - del %appdata%\Temp\react-native-* & cd android & gradlew clean & cd .. & del node_modules/ & npm cache clean --force & npm install & npm start -- --reset-cache

	class ParentComponent extends Component {
	constructor() {
	super();

	this.state = {
	data : [
	{id : 1, date : "2014-04-18", total : 121.0, status : "Shipped", name : "A", points: 5, percent : 50},
	{id : 2, date : "2014-04-21", total : 121.0, status : "Not Shipped", name : "B", points: 10, percent: 60},
	{id : 3, date : "2014-08-09", total : 121.0, status : "Not Shipped", name : "C", points: 15, percent: 70},
	{id : 4, date : "2014-04-24", total : 121.0, status : "Shipped", name : "D", points: 20, percent : 80},