The markup a user of your component writes. This DOM lives outside the component's shadow DOM. It is the element's actual children.

In this case, the component will use black as the background value since the user provided it. Otherwise, it would default to #9E9E9E.

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Closed mode prevents your custom element code from accessing its own shadow DOM. That's complete fail. Instead, you'll have to stash a reference for later if you want to use things like querySelector(). This completely defeats the original purpose of closed mode!

You don't have to author web components that use shadow DOM. But when you do, you take advantage of its benefits (CSS scoping, DOM encapsulation, composition) and build reusable custom elements, which are resilient, highly configurable, and extremely reusable. If custom elements are the way to create a new HTML (with a JS API), shadow DOM is the way you provide its HTML and CSS. The two APIs combine to make a component with self-contained HTML, CSS, and JavaScript.

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Category Shop Lighting · Category Ceiling Lights · Category Wall Lights · Category Outdoor Lights · Category Fans · Category Home Decor · Category On Sale.

Peddler's Village Logo · Inn · Food ... The holiday magic starts when Village-wide lights are switched on at Grand Illumination Celebration on November 15.

Inheritable styles (background, color, font, line-height, etc.) continue to inherit in shadow DOM. That is, they pierce the shadow DOM boundary by default. If you want to start with a fresh slate, use all: initial; to reset inheritable styles to their initial value when they cross the shadow boundary.

Closed mode makes your component less flexible for end users. As you build web components, there will come a time when you forget to add a feature. A configuration option. A use case the user wants. A common example is forgetting to include adequate styling hooks for internal nodes. With closed mode, there's no way for users to override defaults and tweak styles. Being able to access the component's internals is super helpful. Ultimately, users will fork your component, find another, or create their own if it doesn't do what they want :(

:host-context() matches the component if it or any of its ancestors matches . A common use for this is theming based on a component's surroundings. For example, many people do theming by applying a class to or :

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Over the years I've learned a thing or two about authoring web components. I think you'll find some of these tips useful for authoring components and debugging shadow DOM.

Throughout this article, I'll be referring to a demo component () and referencing code snippets from it. If your browser supports the APIs, you should see a live demo of it just below. Otherwise, check out the full source on Github.

Shadow DOM composition introduces a bunch of new fundamentals in web development. Before getting into the weeds, let's standardize on some terminology so we're speaking the same lingo.

If you've been following web components for the last couple of years, you'll know that Chrome 35+/Opera have been shipping an older version of shadow DOM for some time. Blink will continue to support both versions in parallel for some time. The v0 spec provided a different method to create a shadow root (element.createShadowRoot instead of v1's element.attachShadow). Calling the older method continues to create a shadow root with v0 semantics, so existing v0 code won't break.

In our world of web development, composition is how we construct apps, declaratively out of HTML. Different building blocks (