A few weeks ago, Zach Leatherman began discussing his plans to add web component support to Eleventy. Starting with his announcement post, Adding Components to Eleventy with WebC, developers can now start working with a plugin, WebC, to test out this new support. The plugin docs have a great explainer as to why this support is being added, but to me it mainly boils down - running our web components during server build and not on the client-side with JavaScript. Now, so far, my own experiments with web components have been fairly simple, small things, so I'm not too concerned about the client-side impact, but heck, if we can ship no JavaScript, that's better than a small amount.

I will say that while the WebC docs are fairly extensive, I am struggling to wrap my head around it completely now. To be honest, I struggled with Eleventy Serverless too, so I figure I just need to build out a few demos and I think I I'll grok it better. As always, I blog what I learn so I hope this entry (and any further ones) helps others.

I don't want to repeat the docs so I won't walk you through installation and the like, that's all fairly simple, but I do want to point out a few things that caused me trouble at first.

By default, when you add WebC to an Eleventy project, it does not scan for and automatically add in web components. This is covered but (imo) rather late in the docs. When I'm learning something I absolutely do not read to the of the page. As soon as I feel like I can play, I do, and if an important detail is a bit late in the doc, I typically end up screwing something up. ;)

You can add support for a specific or glob of web components three ways, but for now I'll focus on two. You can either define a glob of web components in front matter (at the template or directory level), or as a configuration option. While the first code sample shows the default behavior:

const pluginWebc = require("@11ty/eleventy-plugin-webc");

module.exports = function(eleventyConfig) {

You will most likely want to start off by having Eleventy automatically scan a folder of web components like so:

const pluginWebc = require("@11ty/eleventy-plugin-webc");

module.exports = function(eleventyConfig) {
	eleventyConfig.addPlugin(pluginWebc, {
	    components: "_includes/components/**/*.webc"

By the way, the exact folder doesn't really matter. I used the above based on examples from the docs, but I think going forward I'll use something like _components to match the style used by data and include files in Eleventy.

The next thing that caused me trouble was creating a web component that was dynamic based on attributes. I think my issue was that I was thinking that Liquid directives and tags would be supported, but that's not the case. You use a new file type, .webc, and while it has support for binding attributes via a :name, it isn't really a template language like Liquid. So for example, I couldn't do basic things like conditionals. Here's an example of the simple level you can do with a .webc file, in this case hello-world.webc:

Hello! <span @html="this.name" :alt="this.name"></span>

In this case, I'm binding the alt attribute (which isn't really an attribute of span afaik) as well as defining the inner HTML of a block by using the attribute passed via name, so for example:

<hello-world @name="ray"></hello-world>

This all outputs to:

Hello! <span alt="ray">ray</span>

But like I said, I wanted more flexibility in my component, what I really wanted was Liquid. There is a way to do that, just wrap your component with:

<template webc:type="11ty" 11ty:type="liquid">
stuff here

I think for now my plan is to just use this as a basis for my components, unless I know for sure I don't need conditions and looping.

As I said - I'm pretty new to this so I expect how I do things will change as I learn.

That's pretty much the main things that causes me problems so far, so let's look at a demo!

A Placeholder WebC Example #

Back a few days ago, I blogged about a placeholder web component that made use of dynamic SVG to render simple placeholder images. It was pretty simple, but actually practical I think. How would I convert that code to a server-side rendered WebC component? I basically just switched from JavaScript to Liquid:

<template webc:type="11ty" 11ty:type="liquid">
{% if width == blank %}
	{% assign width = "199" %}
{% endif %}
{% if height == blank %}
	{% assign height = "199" %}
{% endif %}

<svg ns="http://www.w3.org/2000/svg" 
	height="{{height}}" viewbox="0 0 {{width}} {{height}}">
	<rect width="100%" height="100%" fill="#ff0000"></rect>
	{% if text %}
	<text x="50%" y="50%" dominant-baseline="middle" text-anchor="middle">{{ text }}</text>
	{% endif %}

For comparison's sake, here's the JavaScript one:

const ns = 'http://www.w3.org/2000/svg';

class PlaceHolder extends HTMLElement {

	constructor() {


		const shadow = this.attachShadow({mode:'open'});

		this.width = 250;
		this.height = 250;
		this.bgcolor = '#c0c0c0';

		if(this.hasAttribute('width')) this.width = parseInt(this.getAttribute('width'), 10);
		if(this.hasAttribute('height')) this.height = parseInt(this.getAttribute('height'), 10);
		if(this.hasAttribute('bgcolor')) this.bgcolor = this.getAttribute('bgcolor');

		const wrapper = document.createElementNS(ns, 'svg');
		wrapper.setAttribute('width', this.width);
		wrapper.setAttribute('height', this.height);
		wrapper.setAttribute('viewBox', `0 0 ${this.width} ${this.height}`);

		const rect = document.createElementNS(ns, 'rect');
		rect.setAttribute('width', '100%');
		rect.setAttribute('height', '100%');
		rect.setAttribute('fill', this.bgcolor);

		if(this.getAttribute('text')) {
			const text = document.createElementNS(ns, 'text');
			text.setAttribute('x', '50%');
			text.setAttribute('y', '50%');
			text.setAttribute('dominant-baseline', 'middle');
			text.setAttribute('text-anchor', 'middle');
			text.textContent = this.getAttribute('text');


customElements.define('place-holder', PlaceHolder);

I have to say - as much as I don't mind the JavaScript interface for working with web components (and I still have a lot of exploring to do), that Liquid/HTML version is a heck of a lot simpler! Basically - check and default my height and width and just output SVG, with a conditional block inside.

I added this to my components directory, and then in an Eleventy index.webc file, used it like so:

<h3>No Tags</h3>


<h3>Specified w,h, and text.</h3>
<place-holder width="250" height="300" text="ray"></place-holder>

I did NOT include a JavaScript file, I don't need to. The output in _site looks like so:

<h3>No Tags</h3>



<svg ns="http://www.w3.org/2000/svg" width="199" height="199" viewBox="0 0 199 199">
	<rect width="100%" height="100%" fill="#ff0000"></rect>


Specified w,h, and text. <br>

<svg ns="http://www.w3.org/2000/svg" width="250" height="300" viewBox="0 0 250 300">
	<rect width="100%" height="100%" fill="#ff0000"></rect>
	<text x="50%" y="50%" dominant-baseline="middle" text-anchor="middle">ray</text>

You'll notice a lot of white space in the output above. While you can fix that with a HTML post processor (see the super simple Eleventy sample code example), it's something I want to see if I can fix myself later. Most importantly though - not a lick of JavaScript!

Want to see it yourself? I decided to give it a try on Glitch, a service I discovered a month or so ago. You can browse a live, working Eleventy site on their service here: https://glitch.com/edit/#!/placeholder-demo. You can view the running version here: https://placeholder-demo.glitch.me/ Give it a shot and let me know what you think.

Edit on 10/17 at 1:13PM: Just a quick note. I got an email from Rian Murnen who pointed out I could help limit the whitespace using Liquid dashes: https://shopify.github.io/liquid/basics/whitespace/. I made this tweak on a fork of the Glitch here: https://glitch.com/edit/#!/screeching-stitch-field You can absolutely see the difference. I could probably shrink the whitespace more but this was a great quick change. Thanks, Rian!

Photo by Mateusz Feliksik on Unsplash