HTMLSlotElement: slotchange event

BaselineWidely available

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

Theslotchange event is fired on anHTMLSlotElement instance (<slot> element) when the node(s) contained in that slot change.

Note:Theslotchange event doesn't fire if the children of a slotted node change — only if you change (e.g., add or delete) the actual nodes themselves.

In order to trigger aslotchange event, one has to set or remove theslot attribute.

This event is not cancelable.

Syntax

Use the event name in methods likeaddEventListener(), or set an event handler property.

addEventListener("slotchange", (event) => { })onslotchange = (event) => { }

Event type

A genericEvent.

Examples

element.setAttribute("slot", slotName);// element.assignedSlot = $slotelement.removeAttribute("slot");// element.assignedSlot = null

The following snippet is taken from ourslotchange example (see it live also).

let slots = this.shadowRoot.querySelectorAll("slot");slots[1].addEventListener("slotchange", (e) => {  let nodes = slots[1].assignedNodes();  console.log(    `Element in Slot "${slots[1].name}" changed to "${nodes[0].outerHTML}".`,  );});

Here we grab references to all the<slot>s, then add aslotchange event listener to the template's second slot — which is the one which has its contents changed in the example.

Every time the element inserted in the slot changes, we log a report to the console saying which slot has changed, and what the new node inside the slot is.