yelouafi

Algebraic Effects in JavaScript part 4 - Implementing Algebraic Effects and Handlers

This is the final part of a series about Algebraic Effects and Handlers.

• Part 1 : continuations and control transfer
• Part 2 : Capturing continuations with Generators
• Part 3 : Delimited continuations
• Part 4 : Implementing Algebraic Effects and handlers

So we've come to the core topic. The reality is that we've already covered most of it in the previous parts. Especially, in the third part, where we saw delimited continuations at work.

Jessidhia

Implementation notes on react's scheduling model as of (shortly before) 16.8.0

While the public API intended for users to use is the scheduler package, the reconciler currently does not use scheduler's priority classes internally.

ReactFiberScheduler has its own internal "mini-scheduler" that uses the scheduler package indirectly for its deadline-capable scheduleCallback.

This is kind of a documentation of implementation details that I suppose will be gone by the end of the year, but what can you do.

pburtchaell

/**
 * VH and VW units can cause issues on iOS devices: http://caniuse.com/#feat=viewport-units
 * 
 * To overcome this, create media queries that target the width, height, and orientation of iOS devices. 
 * It isn't optimal, but there is really no other way to solve the problem. In this example, I am fixing 
 * the height of element `.foo` —which is a full width and height cover image.
 *
 * iOS Resolution Quick Reference: http://www.iosres.com/
 */
 

yelouafi

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.

akhoury

  // for detailed comments and demo, see my SO answer here http://stackoverflow.com/questions/8853396/logical-operator-in-a-handlebars-js-if-conditional/21915381#21915381
  
  /* a helper to execute an IF statement with any expression
    USAGE:
   -- Yes you NEED to properly escape the string literals, or just alternate single and double quotes 
   -- to access any global function or property you should use window.functionName() instead of just functionName()
   -- this example assumes you passed this context to your handlebars template( {name: 'Sam', age: '20' } ), notice age is a string, just for so I can demo parseInt later
   <p>
     {{#xif " name == 'Sam' && age === '12' " }}
       BOOM

rauschma

Strings

String.prototype.*

None of the string methods modify this – they always return fresh strings.

• charAt(pos: number): string ^ES1

  Returns the character at index pos, as a string (JavaScript does not have a datatype for characters). str[i] is equivalent to str.charAt(i) and more concise (caveat: may not work on old engines).

sebmarkbage

import { Component } from "React";

export var Enhance = ComposedComponent => class extends Component {
  constructor() {
    this.state = { data: null };
  }
  componentDidMount() {
    this.setState({ data: 'Hello' });
  }
  render() {

gaearon

/**
 * Stores are just seed + reduce function.
 * Notice they are plain objects and don't own the state.
 */
const countUpStore = {
  seed: {
    counter: 0
  },

  reduce(state, action) {

pmeenan

// Support routines for automatically reporting user timing for common analytics platforms
// Currently supports Google Analytics, Boomerang and SOASTA mPulse
// In the case of boomerang, you will need to map the event names you want reported
// to timer names (for mPulse these need to be custom0, custom1, etc) using a global variable:
// rumMapping = {'aft': 'custom0'};
(function() {
var wtt = function(n, t, b) {
  t = Math.round(t);
  if (t >= 0 && t < 3600000) {
    // Google Analytics

Warry

How to make faster scroll effects?

• Avoid too many reflows (the browser to recalculate everything)
• Use advanced CSS3 for graphic card rendering
• Precalculate sizes and positions

Beware of reflows

The reflow appens as many times as there are frames per seconds. It recalculate all positions that change in order to diplay them. Basically, when you scroll you execute a function where you move things between two reflows. But there are functions that triggers reflows such as jQuery offset, scroll... So there are two things to take care about when you dynamically change objects in javascript to avoid too many reflows: