Jiayi Hu jiayihu

Algebraic Effects in JavaScript part 1 - continuations and control transfer

This is the first post of a series about Algebraic Effects and Handlers.

There are 2 ways to approach this topic:

Denotational: explain Algebraic Effects in terms of their meaning in mathematics/Category theory
Operational: explain the mechanic of Algebraic Effects by showing how they operate under a chosen runtime environment

Both approaches are valuables and give different insights on the topic. However, not everyone (including me), has the prerequisites to grasp the concepts of Category theory and Abstract Algebra. On the other hand, the operational approach is accessible to a much wider audience of programmers even if it doesn't provide the full picture.

Handle CORS Client-side

Cross-origin resource sharing (CORS) is a mechanism that allows restricted resources (e.g. fonts) on a web page to be requested from another domain outside the domain from which the first resource was served. This is set on the server-side and there is nothing you can do from the client-side to change that setting, that is up to the server/API. There are some ways to get around it tho.

Sources : MDN - HTTP Access Control | Wiki - CORS

CORS is set server-side by supplying each request with additional headers which allow requests to be requested outside of the own domain, for example to your localhost. This is primarily set by the header:

Access-Control-Allow-Origin

Last updated: 2016-08-06

Summary: We'll modify the rustc-builtins crate to make all the intrinsics "undefined", then we'll proceed to bootstrap rustc normally. This will cause a linker error while linking rustc because the intrinsics are "undefined". The linker error message will list the intrinsics that are required to link rustc but the linker couldn't "find".

First, we avoid building .so versions of std, rustc et al. because those will also fail to link but the linker error message will list all the intrinsics instead of only the ones that are actually needed to build a Rust program (binary). We do this by removing "dylib" from the

Comprehensive Introduction to @ngrx/store

By: @BTroncone

Also check out my lesson @ngrx/store in 10 minutes on egghead.io!

Update: Non-middleware examples have been updated to ngrx/store v2. More coming soon!

Table of Contents

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

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.

	/*
	This a basic implementation of task cancellation using a Promise extension
	combined with an AbortController. There are 3 major benefits to this implementation:

	1. Because it's just an extension of a Promise the Task is fully
	compatible with the async/await syntax.
	2. By using the abort controller as a native cancellation token
	fetch requests and certain DOM operations can be cancelled inside the task.
	3. By passing the controller from parent tasks to new child tasks an entire
	async chain can be cancelled using a single AbortController.

	<!--
	Complete feature detection for ES modules. Covers:

	1. Static import: import * from './foo.js';
	2. Dynamic import(): import('./foo.js').then(module => {...});

	Demo: http://jsbin.com/tilisaledu/1/edit?html,output

	Thanks to @_gsathya, @kevincennis, @rauschma, @malyw for the help.
	-->

	var str = 'class ಠ_ಠ extends Array {constructor(j = "a", ...c) {const q = (({u: e}) => {return { [`s${c}`]: Symbol(j) };})({});super(j, q, ...c);}}' +
	'new Promise((f) => {const a = function* (){return "\u{20BB7}".match(/./u)[0].length === 2 \|\| true;};for (let vre of a()) {' +
	'const [uw, as, he, re] = [new Set(), new WeakSet(), new Map(), new WeakMap()];break;}f(new Proxy({}, {get: (han, h) => h in han ? han[h] ' +
	': "42".repeat(0o10)}));}).then(bi => new ಠ_ಠ(bi.rd));';

	try {
	eval(str);
	} catch(e) {
	alert('Your browser does not support ES6!')
	}