Introduction to JSON & Mustache Variables

This documentation is provided as a simple introduction to using one of the supported data types and one of the supported PatternEngines. The best reference for this topic is the Mustache documentation but this should provide a good beginner's primer.

Simple Variablespermalink

At its core JSON is a simple key-value store. This means that any piece of data in JSON has a key and a value. The key is the name of an attribute and the value is what should be shown when that attribute is referenced. Here's a simple example:

"src": "../../images/fpo-avatar.png"

In this case the key is src and the value is ../../images/fpo-avatar.png. Let's look at how we might reference this data in a pattern template. Mustache variables are denoted by the double-curly braces (or mustaches).

<img src="{{ src }}" alt="Avatar" />

The Mustache variable is {{ src }}. Note that src matches the name of the key in our JSON example. When the Node version of Pattern Lab compile this template the end result will be:

<img src="../../images/fpo-avatar.png" alt="Avatar" />

Note that {{ src }} was replaced by the value for src found in our JSON example.

Nested Variablespermalink

We may want our JSON file to be a little more organized and our Mustache variable names to be a little more descriptive. For example, maybe we have multiple image sizes that we want to provide image sources for. We might organize our JSON key-values this way:

"square": {
    "src": "../../images/fpo-square.png",
    "alt": "Square"
},
"avatar": {
    "src": "../../images/fpo-avatar.png",
    "alt": "Avatar"
}

Note how their are attributes ( src, alt ) nested within a larger container ( square ). Also note how the attributes are separated by commas. If we wanted to use the attributes for the square image in our pattern we'd write:

<img
	src="{{ square.src }}"
	alt="{{ square.alt }}"
/>

This would compile to:

<img src="../../images/fpo-square.png" alt="Square" />

This nesting makes it easier to read how the attributes are organized in our patterns. The default data.json file has several examples of this type of nesting of attributes.

Rendering HTML in Variablespermalink

You may want to include HTML in your variables. By default, Mustache will convert HTML mark-up to their HTML entity equivalents. For example, our JSON may look like:

"lyrics": "Just <em>good ol' boys</em>, wouldn't change if they could, <strong>fightin'</strong> the system like a true modern day Robin Hood."

Based on our previous Mustache examples you would probably write out your template like so:

<h2>TV Show Lyrics</h2>
<p>{{ lyrics }}</p>

Unfortunately, that would compile as:

<h2>TV Show Lyrics</h2>
<p>
	Just &lt;em&gt;good ol' boys&lt;/em&gt;, wouldn't change if they could,
	&lt;strong&gt;fightin'&lt;/strong&gt; the system like a true modern day Robin Hood.
</p>

In order to make sure the mark-up doesn't get converted you must use triple curly brackets like so:

<h2>TV Show Lyrics</h2>
<p>{{{ lyrics }}}</p>

Now it would compile correctly:

<h2>TV Show Lyrics</h2>
<p>
	Just <em>good ol' boys</em>, wouldn't change if they could,
	<strong>fightin'</strong> the system like a true modern day Robin Hood.
</p>