Progressively is a javascript library for loading images progressively. It’s written entirely in JavaScript so it doesn’t depend on 3rd-party libraries like jQuery. It's super small, < 1.2kB when minified & gzipped! It will load images on when user browse to the page, saving bandwidth & server requests. It is compatible with all modern browsers. Demo
bower install progressively
npm install progressively
<head>
<link src="progressively.min.css">
</head>
<body>
<figure class="progressive">
<img class="progressive__img progressive--not-loaded" data-progressive="img/highQualityImg" src="img/lowQualityImg">
</figure>
<script src="progressively.min.js"></script>
<script>
progressively.init(options);
</script>
</body>The src attribute will contain the lower quality image (< 20kb for ideal cases) and data-progressive attribute will hold the path/url to high quality image. See demo for examples.
The init() API has a few options
Type: Number Default: 300
The throttle is managed by an internal function that prevents performance issues from continuous firing of window.onscroll events. Using a throttle will set a small timeout when the user scrolls and will keep throttling until the user stops. The default is 300 milliseconds.
Type: Number Default: 100 value
The delay function sets the timout value for images to start load asynchronously. Ideally it's value should be low.
Type: Function Arguments: None
The afterload function is callback function which executes when all images have loaded. It is fired when all the image elements have the *--is-loaded class.
Type: Function Arguments: HTMLElement
The imgload function is invoked whenever an image elements finishes loading. It accepts HTMLElement as an argument which is the current element that is loaded.
progressively.init({
delay: 50,
throttle: 300,
imgload: function(elem) {
console.log(elem);
},
afterload: function() {
console.log('All images have finished loading!');
}
});Progressively has a render() method that can be used to make progressively poll your images when you're not scrolling. For instance in some case you want to render your images before/widthout scrolling down to the image, you can use render
Make sure you follow linting guidelines. For bugs or feature request, open an issue. Create a seprate branch by the name of your feature request and then send PR.
MIT license
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