Marko

Custom tags

Custom tags allow you to break up your application UI into encapsulated, reusable components.

Your first custom tag

Let's say we have a page with the following content:

page.marko
<!doctype html>
<html>
<body>
    <h1>Hello World!</h1>
</body>
</html>
<!doctype html>
html
  body
    h1 -- Hello World!

However, this page is getting pretty complex and unmaintainable. Let's split out the content into a separate component. To do this, we'll create a components/ folder and inside it a hello.marko file:

components/hello.marko
<h1>Hello World!</h1>
h1 -- Hello World!

Marko automatically discovers .marko files under a components/ directory, so we can now use the <hello> tag in our page:

page.marko
<!doctype html>
<html>
<body>
    <hello/>
</body>
</html>
<!doctype html>
html
  body
    hello

Now this <hello> tag can be used multiple times, and even on multiple pages. But what if we don't only want to say hello to the world? Let's pass some attributes.

page.marko
<!doctype html>
<html>
<body>
    <hello name="World"/>
</body>
</html>
<!doctype html>
html
  body
    hello name="World"

The component will receive these attributes as input:

components/hello.marko
<h1>Hello ${input.name}!</h1>
h1 -- Hello ${input.name}!

Nice.

How tags are discovered

Marko discovers components relative to the .marko file where a custom tag is used. From this file, Marko walks up directories until it finds a components/ folder which contains a component matching the name of the custom tag. If it reaches the project root without finding anything, it will then check installed packages for the component.

Let's take a look at an example directory structure to better understand this:

components/
    app-header.marko
    app-footer.marko
pages/
    about/
        components/
            team-members.marko
        page.marko
    home/
        components/
            home-banner.marko
        page.marko

The file pages/home/page.marko can use the following tags:

  • <app-header>
  • <app-footer>
  • <home-banner>

And the file pages/about/page.marko can use the following tags:

  • <app-header>
  • <app-footer>
  • <team-members>

The home page can't see <team-members> and the about page can't see <home-banner>. By using nested component/ directories, we've scoped our page-specific components to their respective pages.

Tag directories

In addition to a Marko template, the children of components/ can be a directory with an index.marko template:

components/
    app-header/
        index.marko
        logo.png
        style.css
    app-footer/
        index.marko

Or a directory with a template whose name matches its parent directory:

components/
    app-header/
        app-header.marko
        app-header.style.css
        logo.png
    app-footer/
        app-footer.marko

This allows you to create components that have other files associated with them and keep those files together in the directory structure.

ProTip: You can take advantage of nested components/ directories to create "subcomponents" that are only available to the component that contains them.

components/
    app-header/
        components/
            navigation.marko
            user-info.marko
        app-header.marko
    app-footer/
        app-footer.marko

Using tags from npm

To use tags from npm, ensure that the package is installed and listed in your package.json dependencies:

npm install --save @marko-tags/match-media

Marko discover tags from packages defined in your package.json, so you can start using them right away:

<div>
    <match-media|{ mobile }| mobile="max-width:30em">
        <!-- nice -->
    </match-media>
</div>
div
  match-media|{ mobile }| mobile="max-width:30em"
    <!-- nice -->

Publishing tags to npm

We saw above that tags from npm are automatically discovered. In order to make this work, your package must include a marko.json at the root.

marko.json
{
  "tags-dir": "./dist/components"
}

This example file tells Marko to expose all components directly under the dist/components/ directory to the application using your package.

We recommend adding the marko and components keywords to your package.json so others can find your components. Then npm publish!

Macros

The <macro> tag allows you to create custom tags in the same file that they are used in.

<macro|{ name }| name="welcome-message">
    <h1>Hello ${name}!</h1>
</macro>

<welcome-message name="Patrick"/>
<welcome-message name="Austin"/>
macro|{ name }| name="welcome-message"
  h1 -- Hello ${name}!

welcome-message name="Patrick"
welcome-message name="Austin"

From Variables

If no other tag would be discovered Marko will check for an in scope variable that matches the tag name.

import SomeTag from "./somewhere.marko"

$ const { renderBody } = input;
$ const MyTag = input.href ? "a" : "button";

<SomeTag/>
<MyTag/>
<renderBody/>
import SomeTag from "./somewhere.marko";
$ const { renderBody } = input;
$ const MyTag = input.href ? "a" : "button";

sometag
mytag
renderbody
EDIT

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