J4.x

Web assets

From Joomla! Documentation

This page is a translated version of the page J4.x:Web Assets and the translation is 12% complete.

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Begrip

In de frontend wereld zijn een heleboel assets (middelen) verwant. Ons keepalive script hangt bijvoorbeeld af van het core.js bestand voor het beheer van de instellingen. In Joomla was nooit een makkelijke manier om dit te specificeren, je moest gewoon meerdere bestanden opnemen. Joomla 4 verandert dit met het concept van web assets.

Definitie

Verwante assets worden gedefinieerd in een JSON bestand zoals system/joomla.asset.json#L14-L21

Dit heeft een structuur met een schema definitie (voor validatie), naam, versie, licentie en dan één of meer asset definities. Assets bevatten een lijst met js - en css bestanden die gerelateerd zijn aan de assets en afhankelijkheden. De afhankelijkheden sectie is alleen maar een lijst met assetnamen die noodzakelijk zijn om de assets te laten functioneren. Bijvoorbeeld:

{
  "$schema": "https://developer.joomla.org/schemas/json-schema/web_assets.json",
  "name": "com_example",
  "version": "4.0.0",
  "description": "Joomla CMS",
  "license": "GPL-2.0+",
  "assets": [
    {
      "name": "bar",
      "type": "style",
      "uri": "com_example/bar.css"
    },
    {
      "name": "bar",
      "type": "script",
      "uri": "com_example/bar.js"
    },
    {
      "name": "beer",
      "type": "style",
      "uri": "com_example/beer.css",
      "dependencies": [
        "bar"
      ],
    },
    {
      "name": "beer",
      "type": "script",
      "dependencies": [
        "core",
        "bar"
      ],
      "uri": "com_example/beer.js",
      "attributes": {
        "defer": true,
        "data-foo": "bar"
      }
    }
  ]
}

Het $schema attribuut is een schema definitie bestand dat je in staat stelt je bestand te valideren met behulp van JSON schema. Lees op de de officiële website voor meer informatie hoe json schema validatie werkt.

Let op: Het hebben van joomla.asset.json voor je extensie of template wordt aanbevolen, maar is niet verplicht om WebAssset te laten werken (kijk bij de volgende sectie).

Let op: Het wordt niet aangeraden om een inline asset toe te voegen aan een json bestand, gebruik liever een bestand.

Uitleg van asset stadia

Elke asset heeft 2 stadia: geregistreerd en gebruikt.

Registered is where an asset is loaded into WebAssetRegistry. That means WebAssetManager knows about the existence of these assets, but will not attach them to a document while rendering. All assets loaded from joomla.asset.json is at registered stage.

Used is where an asset is enabled via "$wa->useAsset()" (->useScript(), ->useStyle(), ->registerAndUseX() etc). That means WebAssetManager will attach these assets and their dependencies to a document while rendering.

An asset cannot be used if it was not registered before, this will cause an unknown asset exception.

Register an asset

All known assets loaded and then stored in WebAssetRegistry (to enable/disable an asset item you have to use WebAssetManager, see next section).

Joomla! will look for next assets definition automatically at runtime (in following order):

media/vendor/joomla.asset.json (on first access to WebAssetRegistry)
media/system/joomla.asset.json
media/legacy/joomla.asset.json
media/{com_active_component}/joomla.asset.json (on dispatch the application)
templates/{active_template}/joomla.asset.json

And load them to registry of known assets.

Note: Each following assets definition will override asset items from previous assets definition, by item name.


You can register your own assets definition via WebAssetRegistry:

/** @var Joomla\CMS\WebAsset\WebAssetManager $wa */
$wa = Factory::getApplication()->getDocument()->getWebAssetManager();
$wr = $wa->getRegistry();
$wr->addRegistryFile('relative/path/to/your/joomla.asset.json');

To add a custom asset item at runtime:

$wr->add('script', new Joomla\CMS\WebAsset\WebAssetItem('foobar', 'com_foobar/file.js', ['type' => 'script']));

Or more simply, using WebAssetManager:

$wa->registerScript('foobar', 'com_foobar/file.js');

The new asset item foobar will be added to the registry of know assets, but will not be attached to a document until your code (a layout, template etc) will request it.

To check whether an asset exists:

if ($wa->assetExists('script', 'foobar'))
{
    var_dump('Script "foobar" exists!');
}

Enabling an asset

All asset management in the current Document handled by WebAssetManager, which is accessible with $doc->getWebAssetManager(); By using AssetManager you can enable or disable needed asset easily in Joomla! through a standard methods.

To enable an asset in the page use the useAsset function, for example:

/** @var Joomla\CMS\WebAsset\WebAssetManager $wa */
$wa = Factory::getApplication()->getDocument()->getWebAssetManager();
$wa->useScript('keepalive');

// Or multiple
$wa->useScript('keepalive')
    ->useScript('fields.validate')
    ->useStyle('foobar')
    ->useScript('foobar');

// Add new asset item with dependency and use it
$wa->registerAndUseScript('bar', 'com_foobar/bar.js', [], [], ['core', 'foobar']);

WebAssetManager will look to WebAssetRegistry whether the requested asset exists, and will enable it for current Document instance. Otherwise it will throw an UnknownAssetException.

To disable an asset in the page use the disableAsset function. The example below will disable the jquery-noconflict asset from being loaded.

/** @var Joomla\CMS\WebAsset\WebAssetManager $wa */
$wa = Factory::getApplication()->getDocument()->getWebAssetManager();
$wa->disableScript('jquery-noconflict');

Note: If there are any dependencies to the disabled asset, then this asset will be re-enabled automatically, no matter what.

To check whether asset enabled, and the asset state:

// Checking whether an asset are active (enabled manually or automatically as dependency)
if ($wa->isAssetActive('script', 'foobar'))
{
    var_dump('Script "foobar" are active!');
}

// Checking state
switch($wa->getAssetState('script', 'foobar')){
	case Joomla\CMS\WebAsset\WebAssetManager::ASSET_STATE_ACTIVE:
		var_dump('Active! Was enabled manually');
		break;
	case Joomla\CMS\WebAsset\WebAssetManager::ASSET_STATE_DEPENDENCY:
		var_dump('Active! Was enabled automatically while resolving dependencies');
		break;
	default:
		var_dump('not active!');
}

Overriding an asset

Overriding may be useful when you need to redefine the URI of asset item or its dependencies. As already was noted, each of the following assets definition from joomla.asset.json will override asset items from previous assets definitions, by item name. That means if you provide joomla.asset.json which contain already loaded asset items, they will be replaced with your items. Another way to override in the code is to register an item with the same name. Example, we have "foobar" script, that load com_example/foobar.js library, and we want to use CDN for this exact library:

How it defined in the system initially:

...
{
  "name": "foobar",
  "type": "script",
  "uri": "com_example/foobar.js",
  "dependencies": ["core"]
}
...

To override the URI we define the asset item with "foobar" name in our joomla.asset.json:

...
{
  "name": "foobar",
  "type": "script",
  "uri": "http://foobar.cdn.blabla/foobar.js",
  "dependencies": ["core"]
}
...

Or, register new asset item with AssetManager:

$wa->registerScript('foobar', 'http://fobar.cdn.blabla/foobar.js', [], [], ['core']);

Working with styles

AssetManager allow to manage Stylesheet files. Stylesheet asset item have a type "style".

Example json definition of item in joomla.asset.json:

...
{
  "name": "foobar",
  "type": "style",
  "uri": "com_example/foobar.css"
}
...

Methods to work with styles

AssetManager offers the following methods to work with style files:

/** @var Joomla\CMS\WebAsset\WebAssetManager $wa */
$wa = Factory::getApplication()->getDocument()->getWebAssetManager();

// Attach foobar to the document
$wa->useStyle('foobar');

// Disable foobar from being attached
$wa->disableStyle('foobar');

// Register custom item without json definition
$wa->registerStyle('bar', 'com_example/bar.css', [], ['data-foo' => 'some attribute'], ['some.dependency']);
// And use it later
$wa->useStyle('bar');

// Register and attach a custom item in one run
$wa->registerAndUseStyle('bar', 'com_example/bar.css', [], ['data-foo' => 'some attribute'], ['some.dependency']);

Add inline style

Additionaly to style files, WebAssetManager allows you to add an inline style, and maintain their relation to the file asset. Inline styles may be placed directly before the dependency, after the dependency, or as usual after all styles.

Inline asset may have a name as well as other assets (but not required), the name can be used to retrieve the asset item from a registry, or as a dependency to another inline asset. If the name is not specified then a generated name based on a content hash will be used.

/** @var Joomla\CMS\WebAsset\WebAssetManager $wa */
$wa = Factory::getApplication()->getDocument()->getWebAssetManager();

// Add an inline content as usual, will be rendered in flow after all assets
$wa->addInlineStyle('content of inline1');

// Add an inline content that will be placed after "foobar" asset
$wa->addInlineStyle('content of inline2', ['position' => 'after'], ['data-foo' => 'bar'], ['foobar']);

// Add an inline content that will be placed before "foobar" asset
$wa->addInlineStyle('content of inline3', ['position' => 'before'], [], ['foobar']);

// Named inline asset
$wa->addInlineStyle('content of inline4', ['name' => 'my.inline.asset']);

Note: "foobar" asset should exist in the asset registry, otherwise you will get an unsatisfied dependency exception.

Example above will produce:

...
<style>content of inline3</style>
<link rel="stylesheet" href="foobar.css" />
<style data-foo="bar">content of inline2</style>
...
...
<style>content of inline1</style>
<style>content of inline4</style>
...

If inline asset has multiple dependencies, then will be used last one for positioning. Example:

$wa->addInlineStyle('content of inline1', ['position' => 'before'], [], ['foo', 'bar']);
$wa->addInlineStyle('content of inline2', ['position' => 'after'], [], ['foo', 'bar']);

Will produce:

...
<link rel="stylesheet" href="foo.css" />
<style>content of inline1</style>
<link rel="stylesheet" href="bar.css" />
<style>content of inline2</style>
...

Note: Named inline assets may be a dependency to another inline asset, however it is not recommended to use an inline asset as dependency to non-inline asset. This will work, but this behavior may change in the future. Prefer to use "position" instead.


Working with scripts

AssetManager allow to manage Script files. Script asset item have a type "script". Example json definition of item in joomla.asset.json:

...
{
  "name": "foobar",
  "type": "script",
  "uri": "com_example/foobar.js",
  "dependencies": ["core"]
}
...

Example json definition of ES6 module script, with fallback to legacy:

...
{
  "name": "foobar-legacy",
  "type": "script",
  "uri": "com_example/foobar-as5.js",
  "attributes": {
    "nomodule": true,
    "defer": true
  },
  "dependencies": ["core"]
}
{
  "name": "foobar",
  "type": "script",
  "uri": "com_example/foobar.js",
  "attributes": {
    "type": "module"
  },
  "dependencies": [
    "core", 
    "foobar-legacy"
  ]
}
...

Methods to work with scripts

AssetManager offer next methods to work with script files:

/** @var Joomla\CMS\WebAsset\WebAssetManager $wa */
$wa = Factory::getApplication()->getDocument()->getWebAssetManager();

// Attach foobar to the document
$wa->useScript('foobar');

// Disable foobar from being attached
$wa->disableScript('foobar');

// Register custom item without json definition
$wa->registerScript('bar', 'com_example/bar.js', [], ['defer' => true], ['core']);
// And use it later
$wa->useScript('bar');

// Register and attach a custom item in one run
$wa->registerAndUseScript('bar','com_example/bar.js', [], ['defer' => true], ['core']);

Add inline script

Addittionaly to script files WebAssetManager allow to add an inline script, and maintain their relation to the file asset. Inline script may be placed directly before the dependency, after the dependency, or as usual after all scripts.

Inline asset may have a name as well as other assets (but not required), the name can be used to retrive the asset item form a registry, or as dependecy to another inline asset. If name not specified then will be used generated name based on a content hash.

/** @var Joomla\CMS\WebAsset\WebAssetManager $wa */
$wa = Factory::getApplication()->getDocument()->getWebAssetManager();

// Add an inline content as usual, will be rendered in flow after all assets
$wa->addInlineScript('content of inline1');

// Add an inline content that will be placed after "foobar" asset
$wa->addInlineScript('content of inline2', ['position' => 'after'], ['data-foo' => 'bar'], ['foobar']);

// Add an inline content that will be placed before "foobar" asset
$wa->addInlineScript('content of inline3', ['position' => 'before'], [], ['foobar']);

// Named inline asset
$wa->addInlineScript('content of inline4', ['name' => 'my.inline.asset']);

// Specify script type
$wa->addInlineScript('content of inline5', [], ['type' => 'module']);

Note: "foobar" asset should exist in the asset registry, otherwise you will get an unsatisfied dependency exception.

Example above will produce:

...
<script>content of inline3</script>
<script src="foobar.js"></script>
<script data-foo="bar">content of inline2</script>
...
...
<script>content of inline1</script>
<script>content of inline4</script>
<script type="module">content of inline5</script>
...

If inline asset have a multiple dependencies, then will be used last one for positioning. Example:

$wa->addInlineScript('content of inline1', ['position' => 'before'], [], ['foo', 'bar']);
$wa->addInlineScript('content of inline2', ['position' => 'after'], [], ['foo', 'bar']);

Will produce:

...
<script src="foo.js"></script>
<script>content of inline1</script>
<script src="bar.js"></script>
<script>content of inline2</script>
...

Note: Named inline asset may be as dependency to another inline asset, hovewer it is not recomended to use an inline asset as dependency to non-inline asset. This will work, but this behavior may changes in future. Prefer to use "position" instead.

Working with a web component

Joomla! allows you to use Web Components for your needs. In Joomla! web components are not loaded as regular script, but loaded via Web Component loader so that they are loaded asynchronously. Therefore, a web component asset item must have a flag "webcomponent" set to the boolean "true". In all other aspects, working with web components in AssetManager is the same as working with a "script" asset item.

Example json definition of some web components in joomla.asset.json (as ES6 module):

...
{
  "name": "webcomponent.foobar",
  "type": "style",
  "uri": "com_example/foobar-custom-element.css",
},
{
  "name": "webcomponent.foobar",
  "type": "script",
  "uri": "com_example/foobar-custom-element.js",
  "attributes": {
     "type": "module"
  },
}
...

Example with fallback, for browsers that does not support ES6 "module" feature. Note that the legacy script should have "wcpolyfill" dependency, and module script should have dependency from legacy script:

...
{
  "name": "webcomponent.foobar",
  "type": "style",
  "uri": "com_example/foobar-custom-element.css",
},
{
  "name": "webcomponent.foobar-legacy",
  "type": "script",
  "uri": "com_example/foobar-custom-element-es5.js",
  "attributes": {
    "nomodule": true,
    "defer": true
  },
  "dependencies": [
    "wcpolyfill"
  ]
},
{
  "name": "webcomponent.foobar",
  "type": "script",
  "uri": "com_example/foobar-custom-element.js",
  "attributes": {
    "type": "module"
  },
  "dependencies": [
    "webcomponent.foobar-legacy"
  ]
}
...

Alternatively you can register them in PHP (as ES6 module):

$wa->registerStyle('webcomponent.foobar', 'com_example/foobar-custom-element.css')
    ->registerScript('webcomponent.foobar', 'com_example/foobar-custom-element.js', ['type' => 'module']);

Attach to document:

$wa->useStyle('webcomponent.foobar')
    ->useScript('webcomponent.foobar');

Note: It is preferred to prefix the asset name with "webcomponent." to make it easily to spot, and distinct it from regular scripts in a layout.

Methods to work with web component

All methods to work with a web component are the same as methods to work with script asset item.

Working with a presets

"Preset" is a special kind of asset item that hold a list of items that has to be enabled, in same way as direct call of useAsset() to each of item in the list. Preset can hold mixed types of assets (script, style, another preset, etc), the type should be provided after # symbol and follows after an asset name, example: foo#style, bar#script.

Example json definition of item in joomla.asset.json:

...
{
  "name": "foobar",
  "type": "preset",
  "uri": "",
  "dependencies": [
    "core#script",
    "foobar#style",
    "foobar#script",
  ]
}
...

Methods to work with preset

AssetManager offer next methods to work with preset items:

/** @var Joomla\CMS\WebAsset\WebAssetManager $wa */
$wa = Factory::getApplication()->getDocument()->getWebAssetManager();

// Attach all items from foobar preset to the document
$wa->usePreset('foobar');

// Disable all items from foobar preset from being attached
$wa->disablePreset('foobar');

// Register custom item without json definition
$wa->registerPreset('bar', '', [], [], ['core#script', 'bar#script']);

// And use it later
$wa->usePreset('bar');

// Register and attach a custom item in one run
$wa->registerAndUsePreset('bar','', [], [], ['core#script', 'bar#script']);

Advanced: Custom WebAssetItem class

The default class for all WebAsset items is Joomla\CMS\WebAsset\WebAssetItem.

You are also allowed to use a custom class, which must implement Joomla\CMS\WebAsset\WebAssetItemInterface or extend Joomla\CMS\WebAsset\WebAssetItem.

A custom class can allow you to do advanced actions, for example, including a script file depending on an active language:

class MyComExampleAssetItem extends WebAssetItem
{
	public function getUri($resolvePath = true): string
	{
		$langTag = Factory::getApplication()->getLanguage()->getTag();
		// For script asset use ".js", for style we would use ".css"
		$path    = 'com_example/bar-' . $langTag . '.js';

		if ($resolvePath)
		{
			// For script asset use "script", for style we would use "stylesheet"
			$path = $this->resolvePath($path, 'script');
		}

		return $path;
	}
}

Additionally, implementing Joomla\CMS\WebAsset\WebAssetAttachBehaviorInterface allows you to add a script options (which may depend on the environment) when your asset is enabled and attached to the Document.

class MyFancyFoobarAssetItem extends WebAssetItem implements WebAssetAttachBehaviorInterface
{
	public function onAttachCallback(Document $doc): void
	{
		$user = Factory::getApplication()->getIdentity();
		$doc->addScriptOptions('com_example.fancyfoobar', ['userName' => $user->username]);
	}
}

Important note: An asset item that implements WebAssetAttachBehaviorInterface should be enabled before onBeforeCompileHead event, otherwise 'onAttachCallback' will be ignored.

Defining a custom WebAssetItem class in joomla.asset.json

In joomla.asset.json you can define which Class should be used with specific AssetItem. For this you can use 2 properties namespace and class. namespace can be defined at Root level (then it will be used as default namespace for all Asset items in joomla.asset.json) or in the Item level. For example:

{
  "$schema": "https://developer.joomla.org/schemas/json-schema/web_assets.json",
  "name": "com_example",
  "version": "4.0.0",
  "namespace": "Joomla\Component\Example\WebAsset",
  "assets": [
    {
      "name": "foo",
      "type": "script",
      "class": "FooAssetItem",
      "uri": "com_example/foo.js"
    },
    {
      "name": "bar",
      "type": "script",
      "namespace": "MyFooBar\Library\Example\WebAsset",
      "class": "BarAssetItem",
      "uri": "com_example/bar.js"
    }
  ]
}

Here the asset foo will be associated with class Joomla\Component\Example\WebAsset\FooAssetItem, and bar with class MyFooBar\Library\Example\WebAsset\BarAssetItem.

Note: If namespace are not defined then by default will be used Joomla\CMS\WebAsset. When namespace is defined but empty, then no namespace will be used, only class. Example:

{
  "$schema": "https://developer.joomla.org/schemas/json-schema/web_assets.json",
  "name": "com_example",
  "assets": [
    {
      "name": "foo",
      "type": "script",
      "class": "FooAssetItem",
      "uri": "com_example/foo.js"
    },
    {
      "name": "bar",
      "type": "script",
      "namespace": "",
      "class": "BarAssetItem",
      "uri": "com_example/bar.js"
    }
  ]
}

Here the asset foo will be associated with class Joomla\CMS\WebAsset\FooAssetItem, and bar with class BarAssetItem (without namespace).