bvaughn

This API was removed in React 17

---

Interaction tracing with React

React recently introduced an experimental profiler API. After discussing this API with several teams at Facebook, one common piece of feedback was that the performance information would be more useful if it could be associated with the events that caused the application to render (e.g. button click, XHR response). Tracing these events (or "interactions") would enable more powerful tooling to be built around the timing information, capable of answering questions like "What caused this really slow commit?" or "How long does it typically take for this interaction to update the DOM?".

With version 16.4.3, React added experimental support for this tracing by way of a new NPM package, scheduler. However the public API for this package is not yet finalized and will likely change with upcoming minor releases, so it should be used with caution.

TomRichter

<?xml version="1.0"?>
<TriggernometryExport Version="1">
  <ExportedTrigger Enabled="true" Name="On Wipe" Id="d2f2668d-dfd5-456d-a404-1d2b5cdd18cd" RegularExpression="(wipeout|0038:end|21:([0-9,a-f,A-F]{8}):40000010)" DebugLevel="Inherit" PrevActions="Keep" PrevActionsRefire="Allow" Scheduling="FromFire" PeriodRefire="Allow" RefirePeriodExpression="0">
    <Actions>
      <Action DiscordTts="false" OrderNumber="1" AuraImageMode="Normal" TextAuraAlignment="MiddleCenter" TextAuraFontSize="8.25" TextAuraEffect="None" TextAuraUseOutline="false" Enabled="true" ActionType="EndEncounter" ExecutionDelayExpression="0" Asynchronous="true" DebugLevel="Inherit" RefireInterrupt="false" RefireRequeue="true" SystemBeepFreqExpression="1000" SystemBeepLengthExpression="100" PlaySoundVolumeExpression="100" PlaySoundExclusive="true" PlaySoundMyself="false" PlaySpeechMyself="false" UseTTSVolumeExpression="100" UseTTSRateExpression="0" UseTTSExclusive="true" LaunchProcessWindowStyle="Normal" ExecScriptType="CSharp" MessageBoxIcon

jhubley

davej

Promise.race([
  fetch('/foo'),
  new Promise((_, reject) =>
    setTimeout(() => reject(new Error('Timeout')), 7000)
  )
]);

gaearon

// connect() is a function that injects Redux-related props into your component.
// You can inject data and callbacks that change that data by dispatching actions.
function connect(mapStateToProps, mapDispatchToProps) {
  // It lets us inject component as the last step so people can use it as a decorator.
  // Generally you don't need to worry about it.
  return function (WrappedComponent) {
    // It returns a component
    return class extends React.Component {
      render() {
        return (

harto

'use strict';

describe('mocha before hooks', function () {
	before(() => console.log('*** top-level before()'));
	beforeEach(() => console.log('*** top-level beforeEach()'));
	describe('nesting', function () {
		before(() => console.log('*** nested before()'));
		beforeEach(() => console.log('*** nested beforeEach()'));
		it('is a nested spec', () => true);
	});

inexorabletash

Indexed DB - N-Dimensional Selection

The problem

We have an index with keys of the form:

[ dim1, dim2, dim3, ... ]

e.g. created with:

paulirish

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

JamesMessinger

// This works on all devices/browsers, and uses IndexedDBShim as a final fallback 
var indexedDB = window.indexedDB || window.mozIndexedDB || window.webkitIndexedDB || window.msIndexedDB || window.shimIndexedDB;

// Open (or create) the database
var open = indexedDB.open("MyDatabase", 1);

// Create the schema
open.onupgradeneeded = function() {
    var db = open.result;
    var store = db.createObjectStore("MyObjectStore", {keyPath: "id"});

domenic

Auto-deploying built products to gh-pages with GitHub Actions

This is a set up for projects which want to check in only their source files, but have their gh-pages branch automatically updated with some compiled output every time they push.

A file below this one contains the steps for doing this with Travis CI. However, these days I recommend GitHub Actions, for the following reasons:

• It is much easier and requires less steps, because you are already authenticated with GitHub, so you don't need to share secret keys across services like you do when coordinate Travis CI and GitHub.
• It is free, with no quotas.
• Anecdotally, builds are much faster with GitHub Actions than with Travis CI, especially in terms of time spent waiting for a builder.