Can I process a front matter item like collections processes tags?

[btrem]

11ty collections can process tags whether a post has one tag: foo or whether it has more than one tag: [foo, bar]. I have a front matter variable that might have one value, or more than one, i.e., it might be var: baz or it might bevar: [baz, bat]. Can I use a {% for %} loop to process it either way? In other words, treat var: baz as if var was an array with one item? I tried this:

{% for item in var %}
    // do something with the item 
{% endfor %}

It works when there's more than one value. But when there's only one, in the form var: baz, it processes the value as an array of letters (which makes sense, but it's not what I want). If it can't be done, I can just use

var: [baz]

so not the end of the world. But it'd be nice if I could write it without brackets when there's only 1 item.

[pdehaan]

Interesting... Nunjucks or LiquidJS?
I'm thinking you could do it with a custom filter which checks to see if the tag attribute is an Array or not and wrap it if needed.

[pdehaan]

Yeah, custom filter should work: https://github.com/pdehaan/11ty-1611

  eleventyConfig.addFilter("toArray", value => {
    if (Array.isArray(value)) {
      return value;
    }
    return [value];
  });

Ref: https://github.com/pdehaan/11ty-1611/blob/fa290cb2d9cb0a8a13fd31acf95986aaf9f26e0e/.eleventy.js#L2-L7

Or, if you want a one-liner:

eleventyConfig.addFilter("toArray", value => Array.isArray(value) ? value : [value]);

---

<p>Convert the tag to an array using custom <code>toArray</code> filter:</p>
<ol>
  {% for t in (tag | toArray) %}
  <li>{{ t }}</li>
  {% endfor %}
</ol>

Ref: https://github.com/pdehaan/11ty-1611/blob/fa290cb2d9cb0a8a13fd31acf95986aaf9f26e0e/src/pages/single.njk#L18-L23

[pdehaan]

Interesting... Nunjucks or LiquidJS?

You must be using Nunjucks, because LiquidJS seems to "just work"(tm) and return a single "single" value instead of splitting by character.

But for future travellers, if you are using liquidjs, you'll need to use the toArray filter in an {% assign %} block before looping, as seen below:

<p>But the <code>toArray</code> filter should still work too:</p>
<ol>
  {% assign tags = tag | toArray %}
  {% for t in tags %}
  <li>{{ t }}</li>
  {% endfor %}
</ol>

[Ryuno-Ki]

I think I've saw Eleventy converting it to an array either way under the hood.
Would need to look up the source code, though.

[btrem]

The filter works perfectly. I would not have thought to write a custom filter, because I'm new to 11ty. So this resolves the immediate issue, and hopefully will help me solve other problems in the future.

Thanks for your help.