Simply install the responsive image component using npm.
$ npm i -S @nuclei-components/responsive-image
To use the webcomponent you need to load it into your page, either by bundling it into your js bundle or by simply loading it via a script tag.
As the support for web components is currently still pretty spotty, you probably want to load a polyfill before loading the web component.
I recommend the webcomponentsjs. To make sure the webcomponent is only loaded once the polyfill is done (when using the
webcomponents-loader.js) you will want to wait for the
WebComponentsReady event before loading the web component. This event is always fired, even in browser that fully support web components.
This image will be used as a fill in until the real image is downloaded. It could be something like a very small version of the image or any other fill in.
<responsive-image src="image.jpg" placeholder="placeholder.png"></responsive-image>
The ratio is used to properly scale your image. If you set your
responsive-image to have a width of
100% it will always be resized using the provided ratio, even when the image is not yet loaded.
A ratio can be defined as width to height, e.g.
4:3 or as a percentage value that is calculated like this:
100 * (height / width) e.g.
100 * (3/4) which is
<responsive-image src="image.jpg" ratio="4:3"></responsive-image>
resizing attribute is set to none on a
<responsive-image> the image will not resize to fit the container.
This property is used to indicate how the image should be positioned when part of it is cropped, e.g. position it in the
bottom left corner so that it will overflow on the top and right. The default is
Available options are:
src, srcset & sizes
Just like on any image you can use the
src attribute to define the image src, as well as a combination of
sizes to define responsive media.
active is set to true the image will be lazy-loaded immediately, even when not in view.
If you use the load when in viewport functionality, you can use the
threshold property to define how much of the image needs to be visible in the viewport to trigger a load event. The default is
0, so as soon as 1px of the the offset is in the viewport, the image will be loaded.
offset property defines at what distance from the visible viewport, the image will be loaded. The default offset of
100px means that as soon as the images is within
100px of the viewport, it will be loaded. Set the offset to
0 to disable it.
When an image is loaded it fires the
Polyfill for IntersectionObserver
This packages uses the
IntersectionObserver to detect if an image is in the viewport or not. If you want to use this in browsers that do not support the
IntersectionObserver you need to include a polyfill: https://github.com/WICG/IntersectionObserver/tree/gh-pages/polyfill
If you want to use this package just for its lazy-loading or if you build your own detection which triggers loading by setting
active to true, you do not need to use the polyfill.