HTMLSlotElement: slotchange event

The slotchange event is fired on an HTMLSlotElement instance (<slot> element) when the node(s) contained in that slot change.

Note: the slotchange 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.

Bubbles Yes
Cancelable No
Interface Event
Event handler property None

In order to trigger a slotchange event, one has to set or remove the slot attribute.

Examples

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

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

let slots = this.shadowRoot.querySelectorAll('slot');
slots[1].addEventListener('slotchange', function(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 a slotchange 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.

Specifications

Specification Status Comment
DOM
The definition of '"Mutation observers" and slotchange event' in that specification.
Living Standard Initial definition

Browser compatibility

BCD tables only load in the browser

See also

HTMLSlotElement