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HTMLSlotElement: assign() method

Baseline 2023
Newly available

Since ⁨March 2023⁩, this feature works across the latest devices and browser versions. This feature might not work in older devices or browsers.

The assign() method of the HTMLSlotElement interface sets the slot's manually assigned nodes to an ordered set of slottables. The manually assigned nodes set is initially empty until nodes are assigned using assign().

Note: You cannot mix manually (imperative) and named (declarative, automatic) slot assignments. Therefore, for this method to work, the shadow tree needs to have been created with the slotAssignment: "manual" option.

Syntax

assign(node1)
assign(node1, node2)
assign(node1, node2, /* …, */ nodeN)

Parameters

node1, …, nodeN

A set of Element or Text nodes.

Return value

None (undefined).

Exceptions

NotAllowedError DOMException

Thrown when calling this method on an automatically assigned slot.

Examples

In the example below, the assign() method is used to display the correct tab in a tabbed application. The function is called and passed the panel to show, which is then assigned to the slot.

function UpdateDisplayTab(elem, tabIdx) {
  const shadow = elem.shadowRoot;
  const slot = shadow.querySelector("slot");
  const panels = elem.querySelectorAll("tab-panel");
  if (panels.length && tabIdx && tabIdx <= panels.length) {
    slot.assign(panels[tabIdx - 1]);
  } else {
    slot.assign();
  }
}

Specifications

Specification
HTML>
# dom-slot-assign>

Browser compatibility

Desktop Mobile
Chrome Edge Firefox Opera Safari Chrome Android Firefox for Android Opera Android Safari on IOS Samsung Internet WebView Android WebView on iOS
assign
92Before Chrome 95, the method accepted any Node instead of just Element and Text.
86–92Accepted sequence<Node> instead of (Element or Text)....
92Before Edge 95, the method accepted any Node instead of just Element and Text.
86–92Accepted sequence<Node> instead of (Element or Text)....
 92
78Before Opera 81, the method accepted any Node instead of just Element and Text.
72–78Accepted sequence<Node> instead of (Element or Text)....
 16.4
92Before Chrome Android 95, the method accepted any Node instead of just Element and Text.
86–92Accepted sequence<Node> instead of (Element or Text)....
 92
65Before Opera Android 67, the method accepted any Node instead of just Element and Text.
61–65Accepted sequence<Node> instead of (Element or Text)....
 16.4
16.0Before Samsung Internet 17.0, the method accepted any Node instead of just Element and Text.
14.0–16.0Accepted sequence<Node> instead of (Element or Text)....
92Before WebView Android 95, the method accepted any Node instead of just Element and Text.
86–92Accepted sequence<Node> instead of (Element or Text)....
 16.4

See also

© 2005–2025 MDN contributors.
Licensed under the Creative Commons Attribution-ShareAlike License v2.5 or later.
https://developer.mozilla.org/en-US/docs/Web/API/HTMLSlotElement/assign