François Romain francoisromain

A better GeoJSON

GeoJSON is a widely-used format for encoding geographic data. It's flexible and human-readable, and because it's just JSON it's easy to integrate into web applications.

But it has some real warts, and if we wanted to we could certainly come up with a better format. After tweeting about my frustrations, I was asked to elaborate. Here goes:

Redundancy

GeoJSON geometries can be one of seven types: Point, MultiPoint, LineString, MultiLineString, Polygon, MultiPolygon and GeometryCollection.

Docker - How to cleanup (unused) resources

Once in a while, you may need to cleanup resources (containers, volumes, images, networks) ...

delete volumes

// see: https://github.com/chadoe/docker-cleanup-volumes

$ docker volume rm $(docker volume ls -qf dangling=true)

$ docker volume ls -qf dangling=true | xargs -r docker volume rm

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

There are many tutorials and articles available online which explain functional programming. Examples show small functions, which are composed into others which again get composed. It is hard to imagine how it would all work, then come the analogies and then the math. While the math is necessary to understand it can be difficult to grasp initially. The analogies on the other hand, (at least for me) are not relatable. Some articles assume the reader knows the different terminologies of FP. Over all I felt it is not inviting to learn.

This introduction is for those who have had a tough time understanding those analogies, taken the plunge to functional programming but still have not been able to swim. This is yet another tutorial on functional programming

Terminology

Functions as first class citizens

Functions are first class means they are just like anyone else, or rather they are not special, they behave the same as say primitives or strings or objects.

How to make a globally available executable script in the scripting language of your choice

Locate the path to the interpreter for the language you are writing in with the which command.
```
  which node
  which python
  which bash
  which ruby
```
Add that path as an interpreter directive (using #!) on the first line of your script. For example if you want to write a node script and which node returned /usr/local/bin/node, the first line of your script should be:

Greensock CSS properties Cheat Sheet

I wrote this as a reference for myself because some of the property names are non-obvious, and there are a number of relevant special properties, and there is no central concise listing of them all in GSAP Docs, other than (in longer form) on the CSSPlugin page.

Standard CSS properties

...are all supported, with hyphenated-names becoming camelCaseNames. Non-animatable properties are also supported but they will be set at the beginning of the tween.

Special mentions:

ffmpeg

Converting Audio into Different Formats / Sample Rates

Minimal example: transcode from MP3 to WMA:
ffmpeg -i input.mp3 output.wma

You can get the list of supported formats with:
ffmpeg -formats

You can get the list of installed codecs with:

The introduction to Reactive Programming you've been missing

(by @andrestaltz)

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.

	class EventEmitter {
	constructor() {
	this.events = {};
	}

	on(event, func) {
	if(this.events[event]) {
	this.events[event].push(func);
	} else {
	this.events[event] = [func];

	function xyz_to_ρ (x, y, z) {
	return Math.sqrt((x * x) + (y * y) + (z * z));
	}

	function zρ_to_θ (z, ρ) {
	return Math.acos(z / ρ);
	}

	function yx_to_φ (y, x) {
	return Math.atan(y / x);