ShadowRoot

BaselineWidely available *

This feature is well established and works across many devices and browser versions. It’s been available across browsers since January 2020.

* Some parts of this feature may have varying levels of support.

TheShadowRoot interface of theShadow DOM API is the root node of a DOM subtree that is rendered separately from a document's main DOM tree.

You can retrieve a reference to an element's shadow root using itsElement.shadowRoot property, provided it was created usingElement.attachShadow() with themode option set toopen.

Instance properties

ShadowRoot.activeElementRead only: Returns theElement within the shadow tree that has focus.
ShadowRoot.adoptedStyleSheets: Add an array of constructed stylesheets to be used by the shadow DOM subtree.These may be shared with other DOM subtrees that share the same parentDocument node, and the document itself.
ShadowRoot.clonableRead only: A boolean that indicates whether the shadow root is clonable.
ShadowRoot.delegatesFocusRead only: A boolean that indicates whether the shadow root delegates focus if a non-focusable node is selected.
ShadowRoot.fullscreenElementRead only: The element that's currently in full screen mode for this shadow tree.
ShadowRoot.hostRead only: Returns a reference to the DOM element theShadowRoot is attached to.
ShadowRoot.innerHTML: Sets or returns a reference to the DOM tree inside theShadowRoot.
ShadowRoot.modeRead only: The mode of theShadowRoot, eitheropen orclosed.This defines whether or not the shadow root's internal features are accessible from JavaScript.
ShadowRoot.pictureInPictureElementRead only: Returns theElement within the shadow tree that is currently being presented in picture-in-picture mode.
ShadowRoot.pointerLockElementRead only: Returns theElement set as the target for mouse events while the pointer is locked.null if lock is pending, pointer is unlocked, or if the target is in another tree.
ShadowRoot.serializableRead only: A boolean that indicates whether the shadow root is serializable.A serializable shadow root inside an element will be serialized byElement.getHTML() orShadowRoot.getHTML() when itsoptions.serializableShadowRoots parameter is settrue.This is set when the shadow root is created.
ShadowRoot.slotAssignmentRead only: Returns a string containing the type of slot assignment, eithermanual ornamed.
ShadowRoot.styleSheetsRead only: Returns aStyleSheetList ofCSSStyleSheet objects for stylesheets explicitly linked into, or embedded in a shadow tree.

Instance methods

ShadowRoot.getAnimations(): Returns an array of allAnimation objects currently in effect, whose target elements are descendants of the shadow tree.
ShadowRoot.getSelection()Non-standard: Returns a Selection object representing the range of text selected by the user, or the current position of the caret.
ShadowRoot.elementFromPoint()Non-standard: Returns the topmost element at the specified coordinates.
ShadowRoot.elementsFromPoint()Non-standard: Returns an array of all elements at the specified coordinates.
ShadowRoot.setHTML(): Provides an XSS-safe method to parse and sanitize a string of HTML into aDocumentFragment, which then replaces the existing tree in the shadow DOM.
ShadowRoot.setHTMLUnsafe(): Parses a string of HTML into a document fragment, without sanitization, which then replaces the shadowroot's original subtree. The HTML string may include declarative shadow roots, which would be parsed as template elements the HTML was set usingShadowRoot.innerHTML.

Events

The following events are available toShadowRoot via event bubbling fromHTMLSlotElement:

HTMLSlotElementslotchange event: An event fired when the node(s) contained in that slot change.

Examples

The following snippets are taken from ourlife-cycle-callbacks example (see it live also), which creates an element that displays a square of a size and color specified in the element's attributes.

Inside the<custom-square> element's class definition we include some life cycle callbacks that make a call to an external function,updateStyle(), which actually applies the size and color to the element. You'll see that we are passing itthis (the custom element itself) as a parameter.

class Square extends HTMLElement {  // …  connectedCallback() {    console.log("Custom square element added to page.");    updateStyle(this);  }  attributeChangedCallback(name, oldValue, newValue) {    console.log("Custom square element attributes changed.");    updateStyle(this);  }  // …}

In theupdateStyle() function itself, we get a reference to the shadow DOM usingElement.shadowRoot.From here we use standard DOM traversal techniques to find the<style> element inside the shadow DOM and then update the CSS found inside it:

function updateStyle(elem) {  const shadow = elem.shadowRoot;  const childNodes = shadow.childNodes;  for (const node of childNodes) {    if (node.nodeName === "STYLE") {      node.textContent = `div {  width: ${elem.getAttribute("l")}px;  height: ${elem.getAttribute("l")}px;  background-color: ${elem.getAttribute("c")};}      `;    }  }}