A custom element that automatically renders a thumbhash placeholder for your lazy-loaded images
thumbhash-custom-element.netlify.app
This package is intended for frontend-only use only. It assumes you have already pre-generated your thumbhashes on the server or during an SSG build step. Many server-side libraries already provide convenience functions that will generate a thumbhash data URI for you. This is fine for pages with a few images, but will quickly increase the size of your html if you have more images. This is where thumbhash-custom-element comes in. All data-heavy calculation will be executed on the frontend, keeping your html small.
Install from npm and import it into your bundle:
npm i @hirasso/thumbhash-custom-elementimport { ThumbHashElement } from "@hirasso/thumbhash-custom-element";
ThumbHashElement.init();Or include the self-initializing production build from a CDN in your <head>:
<head>
<!-- ... -->
<script src="https://unpkg.com/@hirasso/thumbhash-custom-element@0"></script>
</head>Tip
Try to include the script as early as possible on your page. Preferably in the <head>
and without any of the defer, async or type="module" attributes.
Add <thumb-hash> elements with your pre-generated thumbhash strings to your markup:
<figure>
+ <thumb-hash value="YTkGJwaRhWUIt4lbgnhZl3ath2BUBGYA" />
<img src="https://example.com/image.jpg" loading="lazy" width="32" height="32" alt="My large lazy-loaded image">
</figure>Result:
<figure>
+ <thumb-hash value="YTkGJwaRhWUIt4lbgnhZl3ath2BUBGYA" aria-hidden="true">
+ ⏷ #shadow-root (open)
+ <canvas width="32" height="32" style="width: 100%; height: 100%;"></canvas>
+ </thumb-hash>
<img src="https://example.com/image.jpg" loading="lazy" width="32" height="32" alt="My large lazy-loaded image">
</figure>figure,
figure img {
position: relative;
}
thumb-hash {
display: block;
position: absolute;
top: 0;
left: 0;
width: 100%;
height: 100%;
object-fit: cover;
}The default strategy of <thumb-hash> is to render a canvas with the blurry representation of the thumbhash. Other options are img and average:
Add the attribute strategy="img" to render an image with a data URI:
<figure>
+ <thumb-hash strategy="img" value="YTkGJwaRhWUIt4lbgnhZl3ath2BUBGYA" />
<img src="https://example.com/image.jpg" loading="lazy" width="32" height="32" alt="My large lazy-loaded image">
</figure>Result:
<figure>
+ <thumb-hash strategy="img" value="YTkGJwaRhWUIt4lbgnhZl3ath2BUBGYA" aria-hidden="true">
+ ⏷ #shadow-root (open)
+ <img alt="" src="data:image/png;base64,iVBORw0KGgo..." style="width: 100%; height: 100%;">
+ </thumb-hash>
<img src="https://example.com/image.jpg" loading="lazy" width="32" height="32" alt="My large lazy-loaded image">
</figure>Add the attribute strategy="average" to render a div with the average color:
<figure>
+ <thumb-hash strategy="average" value="YTkGJwaRhWUIt4lbgnhZl3ath2BUBGYA" />
<img src="https://example.com/image.jpg" loading="lazy" width="32" height="32" alt="My large lazy-loaded image">
</figure>Result:
<figure>
+ <thumb-hash strategy="average" value="YTkGJwaRhWUIt4lbgnhZl3ath2BUBGYA" aria-hidden="true">
+ ⏷ #shadow-root (open)
+ <div style="width: 100%; height: 100%; background: rgb(111, 51, 0);"></div>
+ </thumb-hash>
<img src="https://example.com/image.jpg" loading="lazy" width="32" height="32" alt="My large lazy-loaded image">
</figure>