query-lazy

A simple jQuery plugin to load elements only when they are needed during scrolling.

Introduction

Set the attribute [data-lazy-src] to an image so that the plugin knows which image should be loaded. It can also be set to other elements to load the background image for the parent element.
If the [data-lazy-url] attribute is set to an element, the content is fetched using ajax.

Make sure that the elements that are loaded via the plugin have a minimum height; otherwise it can happen that all elements are loaded at once.
For example like this:

 .lazy-waiting {
    display: block;
    visibility: hidden;
    min-height: 300px;
}

The plugin provides you with 4 classes to handle this.

1. lazy-waiting This class receives every element that is initialized via the plugin.
2. lazy-loading This class is assigned to each element via which the plugin is requested to load.
3. lazy-done This class is set on every element that has finished loading.

Another example:

body.lazy-done {
    background-size: cover;
    background-repeat: no-repeat;
    background-attachment: fixed;
}

Installation

1. Download the plugin uncompressed, minified
2. Or load the plugin via composer

composer require webcito/query-lazy:dev-main

3. Include the plugin in your project at the end of the body tag. Make sure that jQuery is loaded first.

<script src="./vendor/components/jquery/jquery.min.js"></script>
<script src="./dist/jquery-lazy.min.js"></script>

Usage

Set the attribute [data-lazy-{src,url}] to all elements that should be loaded lazy.

<div data-lazy-src="path/to/img.file">
    <img data-lazy-src="path/to/img.file" src="" alt=""/>
    <div data-lazy-url="./demo/content.html"></div>
</div>

Initialize the plugin

$('[data-lazy-src], [data-lazy-url]').lazy(options);

Options

name	type	default	description
recursive	bool	true	If the value is true, additional lazy elements are searched for and initialized in elements that are loaded via ajax (data-lazy-url).
classStatic	string	'lazy'	The class is set for each element and is not changed further.
classWaiting	string	'lazy-waiting'	This class receives every element that is initialized via the plugin.
classLoading	string	'lazy-loading'	This class is assigned to each element via which the plugin is requested to load.
classDone	string	'lazy-done'	This class is set on every element that has finished loading.
onBeforeLoad	function	(element) => {}	The function is triggered before an element receives its content.
onLoad	function	(element, width, height, scrollY, scrollX) => {}	The function is triggered when an element has received its content.
onError	function	(element) => {}	The function is triggered if an element could not receive its content.
onCompleted	function	() => {}	The function is triggered once all elements have received their content.

Events

name	params	description
beforeLoad.lazy	e	Fires on every element before it is loaded
loaded.lazy	e, width, height, scrollY, scrollX	Fires on any element after it has been loaded

Further information

After an element has been loaded, the attributes data-lazy-src and data-lazy-url are removed from the element.