![]() ![]() the Document object in the case of the normal DOM, or the ShadowRoot in the case of a shadow DOM.Įxtensions to the Event interface related to shadow DOM: posed The Node.isConnected property returns a boolean indicating whether or not the Node is connected (directly or indirectly) to the context object, e.g.The Node.getRootNode() method returns the context object's root, which optionally includes the shadow root if it is available.The Element.shadowRoot property returns the shadow root attached to the specified element, or null if there is no shadow root attached.Īdditions to the Node interface relevant to shadow DOM:.The Element.attachShadow() method attaches a shadow DOM tree to the specified element.Element extensionsĮxtensions to the Element interface related to shadow DOM: Represents the root node of a shadow DOM subtree. Represents any element within a shadow tree that has a matching part attribute. ![]() Pseudo-elements relating specifically to custom elements: ::part Selects the shadow host of the shadow DOM containing the CSS it is used inside (so you can select a custom element from inside its shadow DOM) - but only if the selector given as the function's parameter matches the shadow host's ancestor(s) in the place it sits inside the DOM hierarchy. Selects the shadow host of the shadow DOM containing the CSS it is used inside (so you can select a custom element from inside its shadow DOM) - but only if the selector given as the function's parameter matches the shadow host. Selects the shadow host of the shadow DOM containing the CSS it is used inside. Matches any element that is defined, including built in elements and custom elements defined with fine(). Pseudo-classes relating specifically to custom elements: :defined The "is" option of the Document.createElement() methodĪllows you to create an instance of a standard HTML element that behaves like a given registered custom built-in element. The following extensions are defined: The is global HTML attributeĪllows you to specify that a standard HTML element should behave like a registered custom built-in element. Extensions for creating custom built-in elements Invoked when one of the custom element's attributes is added, removed, or changed. Invoked when the custom element is moved to a new document. Invoked when the custom element is disconnected from the document's DOM. Invoked when the custom element is first connected to the document's DOM. Special callback functions defined inside the custom element's class definition, which affect its behavior: connectedCallback() Returns a reference to the CustomElementRegistry object. Use your custom element wherever you like on your page, just like you would any regular HTML element.Ĭontains functionality related to custom elements, most notably the fine() method used to register new custom elements so they can then be used in your document.Again use regular DOM methods to clone the template and attach it to your shadow DOM. If required, define an HTML template using and.Add child elements, event listeners, etc., to the shadow DOM using regular DOM methods. If required, attach a shadow DOM to the custom element using Element.attachShadow() method.Register your new custom element using the fine() method, passing it the element name to be defined, the class or function in which its functionality is specified, and optionally, what element it inherits from. ![]() Create a class in which you specify your web component functionality, using the class syntax.The basic approach for implementing a web component generally looks something like this: ![]() These can then be reused multiple times as the basis of a custom element's structure. The and elements enable you to write markup templates that are not displayed in the rendered page. In this way, you can keep an element's features private, so they can be scripted and styled without the fear of collision with other parts of the document. Shadow DOMĪ set of JavaScript APIs for attaching an encapsulated "shadow" DOM tree to an element - which is rendered separately from the main document DOM - and controlling associated functionality. Custom elementsĪ set of JavaScript APIs that allow you to define custom elements and their behavior, which can then be used as desired in your user interface. Web Components aims to solve such problems - it consists of three main technologies, which can be used together to create versatile custom elements with encapsulated functionality that can be reused wherever you like without fear of code collisions. This has traditionally not been so easy for custom markup structures - think of the complex HTML (and associated style and script) you've sometimes had to write to render custom UI controls, and how using them multiple times can turn your page into a mess if you are not careful. As developers, we all know that reusing code as much as possible is a good idea. ![]()
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