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Justin Fagnani justinfagnani

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View Scoped-Custom-Element-Registries.md

Scoped Custom Element Definitions

Overview

Scoped Custom Element definitions is an oft-requested feature of Web Components. The global registry is a possible source of name collisions that may arise from coincidence, or from an app trying to define multiple versions of the same element, or from more advanced scenarios like registering mocks during tests, or a component explicitly replacing an element definition for its scope.

Since the key DOM creation APIs are global, scoping definitions is tricky because we'd need a machanis to determind which scope to use. But if we offer scoped versions of these APIs the problem is tractable. This requires that DOM creation code is upgraded to use the new scoped APIs, something that hopefully could be done in template libraries and frameworks.

This proposal adds the ability to construct CustomElementRegistrys and chain them in order to inherit custom element definitions. It uses ShadowRoot as a scope for definitions. ShadowRoot can be associated with a

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justinfagnani / README.md
Last active Apr 24, 2020
Inline JavaScript Modules Definitions
View README.md

Inline JavaScript Module Definitions

Motivation

Domenic's blöcks proposal outlines a way to conveniently define functions that run in another worker/worklet as an inline, non-capturing scope, function body.

Blöcks as proposed have a few open questions and lack a few features that could generalize them to more use cases and with more practical ergonomics.

  • Blöcks don't allow static imports, which makes it harder for them to import neccessary library code. They must rely on dynamic import, which is somewhat more difficult to statically analyzer.
@justinfagnani
justinfagnani / example.ts
Created Mar 4, 2020
Observable LitElement
View example.ts
class ExampleElement extends ObservableLitElement {
@property()
src: string;
@observe('src')
protected async _onSrcChange() {
// fetch the new URL...
}
}
View README.md

This is a reproduction for https://bugs.chromium.org/p/chromium/issues/detail?id=1050221

To reproduce:

  1. Download gist
  2. run npm i
  3. run npm start

Chrome will start, cycle through some async tasks, and print the duration to the document and the terminal running node. On my laptop it takes ~500ms.

Next, run npm start again, bug switch back to the terminal as soon as Chrome launches. There should be enough time to put Chrome in the background before the task completes. The tasks should either never start or never complete. If you put Chrome in the foreground, the tasks will finish quickly.

@justinfagnani
justinfagnani / index.html
Created Dec 14, 2019 — forked from jridgewell/index.html
Creating an TreeWalker, DOM element, and setting a walker's currentNode #jsbench #jsperf (https://jsbench.github.io/#26a49a6033a8a5de00d00e05bf2cb275) #jsbench #jsperf
View index.html
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8"/>
<title>Creating an TreeWalker, DOM element, and setting a walker's currentNode #jsbench #jsperf</title>
<script src="https://cdnjs.cloudflare.com/ajax/libs/benchmark/1.0.0/benchmark.min.js"></script>
<script src="./suite.js"></script>
</head>
<body>
<h1>Open the console to view the results</h1>
View index.html
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8"/>
<title>Directive Implementations</title>
<script src="https://cdnjs.cloudflare.com/ajax/libs/benchmark/1.0.0/benchmark.min.js"></script>
<script src="./suite.js"></script>
</head>
<body>
<h1>Open the console to view the results</h1>
View lottie-player.ts
import lottie from './lib/lottie-import.js';
export class LottiePlayerElement extends HTMLElement {
get src(): string | null {
return this.getAttribute('src');
}
set src(v: string | null) {
if (v == null) {
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justinfagnani / Async Module Initialization.md
Last active Feb 25, 2019
Async Module Initialization with Inline Modules
View Async Module Initialization.md

Async Module Initialization with Inline Modules

The Problem

Modules may need to load non-JS resources that would clearly categorized as dependencies - the module is not truly ready until those resources are (example: templates for UI components). Loading APIs, like fetch() are asynchronous, and there is currently no way to make a module wait for asynchronous calls.

The Problem with Top-Level await

Top-level await, which would block execution within a module on a await expression, has been proposed as a way to solve this problem. It has a critical problem as highlighted here by Rich Harris.

@justinfagnani
justinfagnani / index.html
Last active Jan 2, 2019 — forked from jridgewell/index.html
Text data vs nodeValue #jsbench #jsperf (http://jsbench.github.io/#b962f11b0802e9be42b4b0a660520727) #jsbench #jsperf
View index.html
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8"/>
<title>Text data vs nodeValue #jsbench #jsperf</title>
<script src="https://cdnjs.cloudflare.com/ajax/libs/benchmark/1.0.0/benchmark.min.js"></script>
<script src="./suite.js"></script>
</head>
<body>
<h1>Open the console to view the results</h1>
@justinfagnani
justinfagnani / example.js
Last active Oct 28, 2018
the-platform with the platform
View example.js
import {LitElement, html} from 'lit-element';
import {UseWindowSize} from './useWindowSize.js';
class extends UseWindowSize()(LitElement) {
render() {
return html`
<p>
width: ${window.innerWidth}
height: ${window.innerHeight}
</p>
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