Exploring WebC

A few weeks ago, I was at JamstackConf 22 and WebC was mentioned many times during the talks. It got me curious.

With WebC being pretty new the examples are still limited yet, and since I ran into a few issues, hopefully, sharing my process can help some people in the future.

# Initial Setup

First thing first, you need to have Eleventy 2.0.0-canary.16 or newer. Then you can install the eleventy-plugin following the documentation. I would also recommend adding the no-import config.

The first component I created was a footer. Following the same folder structure as the documentation, I created a site-footer.webc in _includes/components/

The content of that component was a basic footer HTML structure. I used the webc:scoped property on the style tag to scope the styling. On a side note, I'm not able to figure out how to use postCSS in the style tag (mostly to be able to use nesting), but I will look into that later.

<footer class="footer">
    ... a bunch of <div> and <a>

<style webc:scoped>
    CSS goes here

This was pretty straightforward so far.

# How to include a WebC component in a Nunjucks layout?

The first hurdle was how to include that new component into a Nunjucks layout. I don't want to fully rewrite my website in WebC right now, so I can't just include <site-footer></site-footer> in a .webc layout.

The built-in Render plugin of Eleventy is here to help up, but there are a few tricks you need to know to have it fully working.

Previously I had a base.njk layout with the head and the body of my pages. There was also 2 include to import a _footer.njk and _header.njk. So I replaced the njk include of the footer by:

{% renderTemplate "webc" %}
{% endrenderTemplate %}

The footer was rendering, but the CSS was missing.
Well you also need to include:

<style>{{ page.url | webcGetCss | safe }}</style>

But at first, the content of the style tag was empty :(
From reading the following github issue it seems that I'm not the only one running into that problem.

Following the same workaround, I created a root.njk with the first layer of shared tags ( etc..), included the webcGetCss code in the head, then removed everything from the base.njk except the content placeholder and the renderTemplate block of code from above. Tada! it works 🥳.

I have to admit I don't fully understand why we need to do that chaining of layout to make it work, but it's not too bad.

The second issue I ran into, got me stuck for a bit.

# How to pass data from a Nunjucks layout to WebC components?

The next logical component was the nav bar. I created a site-nav.webc, pasted the code from my previous _nav.njk and then realized that I had no idea how to deal with the logic part. At build time the Nav was pulling some site information from a _data/metadata.json file and some collections.all info. More precisely the collection with the eleventyNavigation tag. Navigation Plugin info

Most of the examples I saw at first were either a .webc with only some <template> or only some <script>. I thought I was gonna need to split my nav into smaller components (which would have been fined too). But looking at the repo of 11ty.webc.fun I realized that I can just mix and match.

You can write your HTML in the .webc file and when you need some logic you can plug a script tag.

<script webc:type="render" webc:is="template">
function ()
// your code here
return //html

Initialy, I thought, from looking at examples that I was gonna be able to replace Constant Vallee by ${this.metadata.title}, but I kept getting the following error message: Error with Nunjucks paired shortcode 'renderTemplate' telling me that title was not available.

But thanks to a comment by darth_mall in the 11ty Discord, I understood that if you use the renderTemplate, the context is not inherited and that you need to pass the data. In the documentation they are showing how to pass Front Mater (the part between the --- at the top of the files) data to the renderTemplate. Doing something the following did not work:

  myKey: metadata

It was passing the string "metadata" instead of the actual object.

However, if I passed metadata directly to the renderTemplate, then this contained the data from metadata in the script tag.

{% renderTemplate "webc", metadata %}
{% endrenderTemplate %}

Now my issue was that I needed the data from 2 sources. The _data/metadata.json and the collections 🥺.

Don't try the following code, it does not work. You can pass only one item.

{% renderTemplate "webc", metadata, collections %}
{% endrenderTemplate %}

My solution was to put the two objects into an Object.

{% renderTemplate "webc", data={collections: collections,metadata: metadata} %}
{% endrenderTemplate %}

Now this.data had all the info I needed to build the nav.

In the njk version of the nav, to get the page to include in the navigation I was able to loop on collections.all and filter like this:

{%- for entry in collections.all | eleventyNavigation %}
{%- endfor %}

In the WebC version of the component I was getting all the collection's items (pages, tags etc...). Because the data used by eleventyNavigation is in the Front Matter, I can access that information in the data object of each page. First I get the collections passed in the renderTemplate, then filter the collections.all to only the ones with a data.eleventyNavigation. Finally I use a .map on the leftovers to generate the necessary HTML code. (I probably don't need the eleventyNavigation plugin as long as I keep the variables in the Front Matter of the files 🤔)

<script webc:type="render" webc:is="template">
function () {
let collection = this.data[0].all;
let navigation = collection.filter(page => page.data.eleventyNavigation)
return navigation.map((page) => {
return `<li class="header__item">
<a href="

Now I'm getting the same rendering as before. Except that the nav & the footer from this website are generated from WebC components instead of Nunjucj includes. Next I should probably try to convert the theme switcher and probably the book cards.

If you want to see the full code can explore it on github.

# Thank you

Zach Leatherman for the documentation and the few videos on youtube.
Stephanie Eckles for the guide to WebC.
Evan Sheehan aka darthmall for 11ty.webc.fun and the replies in the 11ty Discord.
Bryan Robinson for his article on renderTemplate.