https://github.com/lbrian/content-visibility

Web Component uses CSS content-visibility and fallback Intersection Observer
https://github.com/lbrian/content-visibility

css intersection-observer intersectionobserver-api javascript lit-element lit-html typescript webcomponent webcomponents

Last synced: about 22 hours ago
JSON representation

Web Component uses CSS content-visibility and fallback Intersection Observer

• Host: GitHub
• URL: https://github.com/lbrian/content-visibility
• Owner: LBrian
• License: mit
• Created: 2021-01-04T12:14:58.000Z (about 4 years ago)
• Default Branch: master
• Last Pushed: 2023-03-05T18:43:35.000Z (almost 2 years ago)
• Last Synced: 2025-02-20T14:51:57.433Z (about 23 hours ago)
• Topics: css, intersection-observer, intersectionobserver-api, javascript, lit-element, lit-html, typescript, webcomponent, webcomponents
• Language: HTML
• Homepage:
• Size: 34.5 MB
• Stars: 28
• Watchers: 4
• Forks: 2
• Open Issues: 16
• Metadata Files:
  • Readme: README.md
  • License: LICENSE

Awesome Lists containing this project

README

        
# content-visibility 

[![Published on webcomponents.org](https://img.shields.io/badge/webcomponents.org-published-blue.svg)](https://www.webcomponents.org/element/content-visibility)

![npm 7.0.15](https://img.shields.io/badge/npm-7.0.15-blue)

![Typescript](https://img.shields.io/badge/typescript-4.1.3-blue)

![Lit-Element](https://img.shields.io/badge/LitElement-2.3.1-blue)

`` is a simple **web component** encapsulates modern CSS properties `content-visibility` and Web API **Intersection Observer API** to provide cross-browsers solution to skip rendering (layout & painting) elements until it is needed (appears on the viewport) to boosts page performance.

CSS `content-visibility` is only supported on Chrome 85+, Chrome Android 85+ and Opera 71+ but not Firefox, Safari and IE unfortunately, see [web.dev](https://web.dev/content-visibility/). **Intersection Observer API** supports pretty much all browsers except **IE**, thus an intersection observer [polyfill](https://www.npmjs.com/package/intersection-observer) is included for compatible on IE.

Basically, all children inside it will only be renderred after it appears on viewport.

```html

  {children will not be rendered when outside the first viewport}

```

## Compatibility

  

    

    

    

    

    

    

  

# Getting started

## Install

`npm i content-visibility --save`

## Use in JSX (React/Preact)

```jsx

import 'content-visibility';

const Content = () => {

  return (

    

      ...

      ...

      ...

    

  );

};

```

## properties

### `containIntrinsicSize`

This is will be set as CSS custom variable for `contain-intrinsic-size` if browsers support it. [see](https://web.dev/content-visibility/#specifying-the-natural-size-of-an-element-with-contain-intrinsic-size)

```html

  {children}

```

# Performance results

## Rendering frames

**Safari** comes with `Rendering Frames Timeline` tool helps to measure rendering performance. Let's have a look the rendering frames **without** ``, total `97` rendering frames happened on the first view.

![Rendering Frames - no content-visibility](./images/no-content-visibility.gif?raw=true)

Only `47` rendering frames happened on the first view after integrated with ``

![Rendering Frames - content-visibility](./images/content-visibility-frames.gif?raw=true)

the rest of `50` rendering frames happened when **scorlling to the viewport**

![Rendering Frames - content-visibility scroll](./images/content-visibility-frames-2.gif?raw=true)

## Rendering & Layout time

Generally speaking, we can plausibly say rendering & layout time improved around `40%`, however benchmark results vary depends on sampling size, environments, tools, implementation and etc. Too many factors could impact benchmark results, so this is just a quick sample results to demonstrate the performance differences.

### Chrome 87.0.4280.141

CSS `content-visibility` and `contain-intrinsic-size`

#### Before

![Chrome Before](./images/chrome-before.png?raw=true)

#### After

**Rendering** and **Painting** time reduced around `50%`.

![Chrome After](./images/chrome-after.png?raw=true)

### Firefox 84.0.2

#### Before

![Firefox Before](./images/firefox-before.png?raw=true)

#### After

![Firefox After](./images/firefox-after.png?raw=true)

# License

Copyright (c) 2021 [Brian YP Liu](https://brianypliu.com/)