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lazy-image-loader

Lazy Image Loader

Build Status Code Climate

Parses the DOM and looks for elements to load images in a deferred manner.

You have to create lazy image elements by the following rules to allow the lazy loader to reach them.

With the following setup, the lazy loader attempts to load an image from a generated url by creating an element and appending it into the lazy element. It tries to calculate the width of the parent element and set the following url as the src attribute of the newly generated element:

So, for example if the width of the parent element is 400px, the url becomes: http://example.com/400/path/to/your/image.jpg

<div class="lazy-image" data-path="/path/to/your/image.jpg"></div>
 
<script>
  $(window).load(function () {
    if ('LazyImageLoader' in window) {
      LazyImageLoader('http://example.com', {});
    }
  });
</script> 

Installation

It supports browser environments and CommonJS format.

using npm:

$ npm install lazy-image-loader

in the browser:

<script src="lazy-image-loader.js"></script>

Usage

It's recommended to wait for the window's onload event.

lazy(host, [options]);

Lazy loader prefers leading slash when you set the path and please avoid to use trailing slash when you set the host.

commonjs:

 
var lazy = require('lazy-image-loader');
var $ = require('jquery');
 
$(window).load(function () {
  lazy('http://example.com', {});
});
 

browser:

<script src="//cdnjs.cloudflare.com/ajax/libs/jquery/2.1.4/jquery.min.js"></script>
<script>
  $(window).load(function () {
    if ('LazyImageLoader' in window) {
      LazyImageLoader('http://example.com', {});
    }
  });
</script> 

Options

  • url (Function) - You can set your own url getter function. It gets two parameters: width and path.
  • className (String) - custom css class selector instead of .lazy-image
  • pathAttribure (String) - custom html attribute name instead of data-path
  • onBeforeSet (Function) - A function which is called before each lazy image loading. The callback gets the img as the first parameter.

A real-life usage example of the onBeforeSet hook:

It's pretty nice to put a blur effect on the image until it gets loaded. Actually, this is what the great antimoderate module does but we use a css approach here.

style.css

.blurry {
  filter: blur(3px);
}

my-blurry-module.js

var lazy = require('lazy-image-loader');
var loaded = require('image-loaded');
 
lazy({
  onBeforeSet: function(img) {
    img.classList.add('blurry');
      loaded(img, function() {
      img.classList.remove('blurry');
    });
  }
});

License

MIT © Purpose Industries