Web components, so close!
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What is web components, inner structure, how they are connected with each other, what is the current state of web components and what is their future
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Web components, so close!
- 1. Web Components, so close! Oleksandr Zinevych Software Engineer at Datamart Inc.
- 2. Agenda • How our markup looks today? • Web Components will help us! • Inner structure • Simple web component live • Current state, known issues and future plans
- 3. How your frontend code looks like?
- 5. Main problems here • We have too many similar components in our web page that fall under the same semantic structure. To distinguish them from each other, we use classes, IDs, or other attributes. • The available list of semantic tags are simply not enough to target the wide variety of components that constitute our design. As a result, we fall back to traditional tags like div or span.
- 7. • Web Components are a set of standards currently being produced by Google engineers as a W3C specification that allow for the creation of reusable widgets or components in web documents and web applications. • The intention behind them is to bring component-based software engineering to the WWW.
- 8. Web Components aren’t new! (1998) HTML Components - was proposed and implemented by Microsoft starting in IE5.5 (obsoleted in IE10). XBL(2001) and XBL2(2007) - was proposed by Mozilla as a companion to their XUL user-interface language.
- 9. Web Components TEMPLATES SHADOW DOM HTML IMPORT CUSTOM ELEMENTS <template id=“”> </template> div #document fragment span <link rel=“import” href=“doc.html”> <my-elem></my-elem>
- 10. Templates
- 11. • The HTML template element <template> is a mechanism for holding client-side content that is not to be rendered when a page is loaded but may subsequently be instantiated during runtime using JavaScript.
- 12. • Its content is effectively inert until activated. • Script doesn't run, images don't load, audio doesn't play,...until the template is used. • Content is considered not to be in the document. • Templates can be placed anywhere inside of <head>, <body>, or <frameset> and can contain any type of content.
- 14. Gotchas, you need to remember • You cannot prerender a template(preload assets, process JS or etc.) • Avoid nested template because of activation.
- 15. Shadow DOM
- 16. DOM tree encapsulation • DOM nodes can already “host” hidden DOM • The hidden DOM cannot be accessed from outside JS • Styles defined in Shadow DOM are scoped by default
- 17. How can you see it?
- 19. • Shadow Host: is the DOM element which is hosting the Shadow DOM subtree or it is the DOM node which contains the Shadow Root. • Shadow Root: is the root of the DOM subtree containing the shadow DOM nodes. • Shadow DOM: allows for multiple DOM subtrees to be composed into one larger tree while rendering.
- 21. Lets create it!
- 22. Why Shadow DOM? • Separate your Content from Presentation (<content> tag) • Style and DOM encapsulation
- 23. Think about how you load HTML on the web?
- 25. How it looks?
- 26. Recommendations • Concatenate imports • Do not forget about browser caching • Imports block rendering(use async if needed)
- 27. Custom Elements
- 28. Simple creation
- 29. Advanced creation • You can extend both native and previously created custom elements:
- 30. Events • createdCallback – when an instance of the element is created • attachedCallback - when an instance was inserted into the document • detachedCallback – when an instance was removed from the document • attributeChangedCallback – when an attribute was added, removed, or updated
- 31. How it works?
- 33. Web Components are coming! • At the beginning it was just a Google intention. For now discussions about specifications are between Mozilla, Google, Apple, Microsoft. • The whole vision of Web Components is not fully realized and discussed by all browser vendors. But we can experiment with them now. • Web Components are a transformative step forward for the web
- 34. Browsers are not ready • Shadow DOM spec compromise • Custom elements, HTML Imports are still controversial • Templates are broadly supported
- 35. Future of Web Components Declarative shadow DOM Fully Isolated Components Accessibility primitives Unified native control styling CSS Parts styling Parser customization
- 36. Thanks for attention! • E-mail: aleksanderzinewicz@gmail.com • Twitter: @a_zinewicz • Facebook: @aleksander.zinewicz • Skype: oleksandr.zinevych@outlook.com