Given a string value for a named boolean attribute, return
true if the
value is either: a) the empty string, or b) a case-insensitive match for the
This is native HTML behavior; see the MDN documentation on boolean attributes for the reasoning.
Given a null value, this return
Given a boolean value, this return the value as is.
Return the closest focusable node that's either the node itself (if it's focusable), or the closest focusable ancestor in the composed tree.
If no focusable node is found, this returns null.
Return the ancestors of the given node in the composed tree.
In the composed tree, the ancestor of a node assigned to a slot is that slot, not the node's DOM ancestor. The ancestor of a shadow root is its host.
Returns true if the first node contains the second, even if the second node is in a shadow tree.
The standard Node.contains() function does not account for Shadow DOM, and returns false if the supplied target node is sitting inside a shadow tree within the container.
Node– The container to search within.
Node– The node that may be inside the container.
boolean - True if the container contains the target node.
Return the first focusable element in the composed tree below the given root. The composed tree includes nodes assigned to slots.
This heuristic considers only the document order of the elements below the root and whether a given element is focusable. It currently does not respect the tab sort order defined by tabindex values greater than zero.
Node– the root of the tree in which to search
HTMLElementnull - the first focusable element, or null if none
mousedown events on the
origin element and prevent the default
behavior from setting the focus on that element. Instead, put the focus on
target element (or, if the
target is not focusable, on the target's
closest focusable ancestor).
If this method is called again with the same
origin element, the old
forwarding is overridden, and focus will now go to the new
target parameter is
null, focus handling will be removed from the
Search a list element for the item that contains the specified target.
When dealing with UI events (e.g., mouse clicks) that may occur in subelements inside a list item, you can use this routine to obtain the containing list item.
NodeList|Array.– A list element containing a set of items
Node– A target element that may or may not be an item in the list.
number - The index of the list child that is or contains the
indicated target node. Returns -1 if not found.
Return true if the event came from within the node (or from the node itself); false otherwise.
Node– The node to consider in relation to the event
Event– The event which may have been raised within/by the node
boolean - True if the event was raised within or by the node
Returns the set that includes the given node and all of its ancestors in the composed tree. See composedAncestors for details on the latter.
Set an internal state for browsers that support the
:state selector, as
well as an attribute of the same name to permit state-based styling on older
When all browsers support that, we'd like to deprecate use of attributes.
Adds or removes the element's
childNodes as necessary to match the nodes
indicated in the
This operation is useful in cases where you maintain your own set of nodes which should be rendered as the children of some element. When you insert or remove nodes in that set, you can invoke this function to efficiently apply the new set as a delta to the existing children. Only the items in the set that have actually changed will be added or removed.
Element– the element to update
NodeList|Array.– the set of nodes to apply