https://github.com/tvler/lazy-progressive-enhancement

A lazy image loader designed to enforce progressive enhancement and valid HTML.
https://github.com/tvler/lazy-progressive-enhancement

lazyload progressive-enhancement

Last synced: 12 days ago
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A lazy image loader designed to enforce progressive enhancement and valid HTML.

• Host: GitHub
• URL: https://github.com/tvler/lazy-progressive-enhancement
• Owner: tvler
• License: mit
• Created: 2016-04-09T23:29:16.000Z (over 8 years ago)
• Default Branch: master
• Last Pushed: 2020-05-29T22:32:50.000Z (over 4 years ago)
• Last Synced: 2024-10-23T01:13:55.745Z (21 days ago)
• Topics: lazyload, progressive-enhancement
• Language: JavaScript
• Homepage: http://tylerdeitz.co/lazy-progressive-enhancement/
• Size: 15.7 MB
• Stars: 190
• Watchers: 4
• Forks: 10
• Open Issues: 4
• Metadata Files:
  • Readme: readme.md
  • License: license

Awesome Lists containing this project

README

        
# Lazy Progressive Enhancement

### [Download, copy-paste, whatever ;)](lazy-progressive-enhancement.min.js)

**[View website](http://tylerdeitz.co/lazy-progressive-enhancement/)**

A lazy image loader designed to enforce progressive enhancement and valid HTML.

Not a framework, not a library, just a function (with clean af markup).

``` html



```

``` js

loadMedia(

   element,

   onload,

   scroll

)

```

**element:** *CSS String | NodeList | Element (optional)* – loads all images if not set

**onload:** *Function (optional)*

**scroll:** *Boolean (optional)* – loads image when visible

### Benefits of Lazy Progressive Enhancement

 - Designed to enforce progressive enhancement and valid HTML.

 - Written in pure JS -- no dependencies.

 - Not a framework, not a library, just a function.

 - Works with responsive `srcset` images.

 - Works with iframes.

Other lazy loaders promote [invalid HTML](https://www.w3.org/TR/html5/embedded-content-0.html#attr-img-src) by omitting the src attribute, or aren't compatible for users without javascript.

### Contents

 - [Basic Usage](#basic-usage)

 - [Load Specific Images](#load-specific-images)

 - [onload Function](#onload-function)

 - [Scroll-Based Loading](#scroll-based-loading)

 - [Build](#build)

## Basic Usage

By default, the function targets every `noscript` element on the page.

Any attributes the image has in noscript (`class` / `id` / `alt` / etc) are kept.

`HTML`

```html



```

`JS`

```js

loadMedia()

```

`End result HTML`

```html



```

## Load Specific Images

You can specify what images to load by passing in either

 1. A CSS selector string (use if calling the function before `DOMContentLoaded`)

 2. A NodeList of `noscript`s (from something like `document.querySelectorAll`)

 3. A singular `noscript` Element (from something like `document.querySelector`)

`HTML`

```html





```

`JS`

```js

loadMedia('#this-one')

```

`End result HTML`

```html





```

## onload Function

You can hook an onload function for every loaded image

`JS`

```js

loadMedia(null, function() {

   this.classList.add('loaded')

})

```

`End result HTML`

```html



```

## Scroll-Based Loading

There's a default function to load images when they're scrolled into view.

This is a general solution, creating your own scroll-based loading functionality may be more performant.

Will be updated to use [intersection observers](https://github.com/WICG/IntersectionObserver) when it becomes standardized.

`JS`

``` js

loadMedia(null, null, true)

```

## Build

`uglifyjs lazy-progressive-enhancement.js -m --comments > lazy-progressive-enhancement.min.js`

## Thanks

[@agarzola](https://github.com/agarzola), [@raglannyc](https://github.com/raglannyc)

--

[MIT License (MIT)](LICENSE)