slikts

Advanced memoization and effects in React

Memoization is a somewhat fraught topic in the React world, meaning that it's easy to go wrong with it, for example, by [making memo() do nothing][memo-pitfall] by passing in children to a component. The general advice is to avoid memoization until the profiler tells you to optimize, but not all use cases are general, and even in the general use case you can find tricky nuances.

Discussing this topic requires some groundwork about the technical terms, and I'm placing these in once place so that it's easy to skim and skip over:

• Memoization means caching the output based on the input; in the case of functions, it means caching the return value based on the arguments.
• Values and references are unfortunately overloaded terms that can refer to the low-level implementation details of assignments in a language like C++, for example, or to memory

markerikson

[12:03 AM] acemarke: "controlled" and "uncontrolled" inputs
[12:04 AM] acemarke: if I have a plain, normal HTML page, and I put <input id="myTextbox" type="text" /> in my page(edited)
[12:04 AM] acemarke: and I start typing into that textbox
[12:04 AM] acemarke: it remembers what I've typed. The browser stores the current value for that input
[12:05 AM] acemarke: and then sometime later, I can get the actual element, say, const input = document.getElementById("myTextbox"), and I can ask it for its value: const currentText = input.value;
[12:05 AM] acemarke: good so far?
[12:08 AM] acemarke: I'll keep going, and let me know if you have questions
[12:08 AM] lozio: ok, actually I'm reading
[12:09 AM] lozio: good
[12:09 AM] acemarke: so, a normal HTML input field effectively stores its own value at all times, and you can get the element and ask for its value

lontivero

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text.RegularExpressions;
using System.Xml;
using System.Xml.Linq;

namespace GithubWikiDoc
{

hyle

// knockout 2.2.1

ko.utils.arrayFilter                            = function (array, predicate) { /* .. */ }

ko.utils.arrayFirst                             = function (array, predicate, predicateOwner) { /* .. */ }

ko.utils.arrayForEach                           = function (array, action) { /* .. */ }

ko.utils.arrayGetDistinctValues                 = function (array) { /* .. */ }

sstephenson

var detectBackOrForward = function(onBack, onForward) {
  hashHistory = [window.location.hash];
  historyLength = window.history.length;

  return function() {
    var hash = window.location.hash, length = window.history.length;
    if (hashHistory.length && historyLength == length) {
      if (hashHistory[hashHistory.length - 2] == hash) {
        hashHistory = hashHistory.slice(0, -1);
        onBack();