Hidenari Nozaki ghiden

Clojure Destructuring Tutorial and Cheat Sheet

Simply put, destructuring in Clojure is a way extract values from a datastructure and bind them to symbols, without having to explicitly traverse the datstructure. It allows for elegant and concise Clojure code.

Vectors and Sequences

API	Status Codes
[Twitter][tw]	200, 304, 400, 401, 403, 404, 406, 410, 420, 422, 429, 500, 502, 503, 504
[Stripe][stripe]	200, 400, 401, 402, 404, 429, 500, 502, 503, 504
[Github][gh]	200, 400, 422, 301, 302, 304, 307, 401, 403
[Pagerduty][pd]	200, 201, 204, 400, 401, 403, 404, 408, 500
[NewRelic Plugins][nr]	200, 400, 403, 404, 405, 413, 500, 502, 503, 503
[Etsy][etsy]	200, 201, 400, 403, 404, 500, 503
[Dropbox][db]	200, 400, 401, 403, 404, 405, 429, 503, 507

Making chained API Calls using @ngrx/Effects

Purpose

This recipe is useful for cooking up chained API calls as a result of a single action.

Description

In the below example, a single action called POST_REPO is dispatched and it's intention is to create a new repostiory on GitHub then update the README with new data after it is created.
For this to happen there are 4 API calls necessary to the GitHub API:

POST a new repostiry
GET the master branch of the new repository
GET the files on the master branch

Using JavaScript Libraries from ClojureScript

Using JavaScript libraries from ClojureScript involves two distinct concerns:

Packaging the code and delivering it to the browser
Making ClojureScript code that accesses JavaScript libraries safe for advanced optimization

Right now, the only single tool that solves these probems reliably, optimally, and with minimal configuration is shadow-cljs, and so that is what I favor. In paricular, shadow-cljs lets you install npm modules using npm or yarn and uses the resulting package.json to bundle external dependencies. Below I describe why, what alternatives there are, and what solutions I disfavor at this time.

	Each YouTube video has 4 generated images. They are predictably formatted as follows:

	http://img.youtube.com/vi/<insert-youtube-video-id-here>/0.jpg
	http://img.youtube.com/vi/<insert-youtube-video-id-here>/1.jpg
	http://img.youtube.com/vi/<insert-youtube-video-id-here>/2.jpg
	http://img.youtube.com/vi/<insert-youtube-video-id-here>/3.jpg

	The first one in the list is a full size image and others are thumbnail images. The default thumbnail image (ie. one of 1.jpg, 2.jpg, 3.jpg) is:

	http://img.youtube.com/vi/<insert-youtube-video-id-here>/default.jpg

	/*
	This snippet is an example of backpressure implementation in Go.
	It doesn't run in Go Playground, because it starts an HTTP Server.

	The example starts an HTTP server and sends multiple requests to it. The server starts denying
	requests by replying an "X" (i.e. a 502) when its buffered channel reaches capacity.

	This is not the same as rate-limiting; you might be interested in https://github.com/juju/ratelimit
	or https://godoc.org/golang.org/x/time/rate.

	/*
	Parallel processing with ordered output in Go
	(you can use this pattern by importing https://github.com/MarianoGappa/parseq)

	This example implementation is useful when the following 3 conditions are true:
	1) the rate of input is higher than the rate of output on the system (i.e. it queues up)
	2) the processing of input can be parallelised, and overall throughput increases by doing so
	3) the order of output of the system needs to respect order of input

	- if 1 is false, KISS!

	(defn my-component [props context updater]
	(cljs.core/this-as this
	(js/React.Component.call this props context updater)
	;; anything else you want to set-up. use goog.object/set on this
	this))

	(gobj/extend
	(.. my-component -prototype)
	js/React.Component.prototype)

	(ns demo.react-cljs-es6-classes
	(:require [goog.object :as gobj]))

	;; Demo of using bare React using ES6 classes (without createClass or reagent)
	;;
	;; Equivalent of Javascript/JSX:
	;;
	;; class MyComponent extends React.Component {
	;; constructor(props) {
	;; super(props);

	// Add on element with overflow
	-webkit-mask-image: -webkit-radial-gradient(white, black);