silverbullet/website/🔌 Directive.md

---
type: plug
repo: https://github.com/silverbulletmd/silverbullet
---

The directive plug is a built-in plug implementing various so-called “directive” that all take the form of `<!-- #directiveName ... -->` and close with `<!-- /directiveName -->`. Currently the following directives are supported:

* `#query` to perform queries: [[🔌 Directive/Query]]
* `#include` to inline the content of another page verbatim: [[@include]]
* `#use` to use the content of another as a [handlebars](https://handlebarsjs.com/) template: [[@use]]
* `#eval` to evaluate an arbitrary JavaScript expression and inline the result: [[@eval]]


## Include
$include
The `#include` directive can be used to embed another page into your existing one. The syntax is as follows:

    <!-- #include [[page reference]] -->
    
    <!-- /include -->

Whenever the directives are updated, the body of the directive will be replaced with the latest version of the reference page. 

## Use
$use
The `#use` directive can be used to use a referenced page as a handbars template. Optionally, a JSON object can be passed as argument to the template:

    <!-- #use [[template/plug]] {"name": "🔌 Directive", "repo": "https://google.com", "author": "Pete"} -->
    
    <!-- /use -->

which renders as follows:
<!-- #use [[template/plug]] {"name": "🔌 Directive", "repo": "https://google.com", "author": "Pete"} -->
* [[🔌 Directive]] by **Pete** ([repo](https://google.com))
<!-- /use -->
* [ ] #test This is a test task

Note that a string is also a valid JSON value:

So, a template can take, for instance a tag name as an argument:

    <!-- #use [[template/tagged-tasks]] "test" -->
    * [ ] [[🔌 Directive@1537]] This is a test task  #test
    <!-- /use -->

## Eval
$eval
The `#eval` directive can be used to evaluate arbitrary JavaScript expressions. It’s also possible to invoke arbitrary plug functions this way.

**Note:** This feature is experimental and will likely evolve.

A simple example is multiplying numbers:

    <!-- #eval 10 * 10 -->
    100
    <!-- /eval -->

However, you can also invoke arbitrary plug functions, e.g. the `titleUnfurlOptions` function in the `core` plug:

    <!-- #eval core.titleUnfurlOptions() -->
    |id          |name         |
    |------------|-------------|
    |title-unfurl|Extract title|
    <!-- /eval -->

Optionally, you can use a `render` clause to render the result as a template, similar to [[🔌 Directive/Query]]:

    <!-- #eval core.titleUnfurlOptions() render [[template/debug]] -->
    id: title-unfurl
    name: Extract title
    ---
    <!-- /eval -->