Element: slot property - Web APIs

The Shadow DOM spec was rewritten as v1, which included the slot> element as the way light DOM nodes would get displayed within a shadow tree

Overview The slot> element acts as a placeholder within a web component's Shadow DOM, which can be filled with custom markup from the main document

elements the awakening slot Overview The slot> element acts as a placeholder within a web component's Shadow DOM, which can be filled with custom markup from the main document

elements slot An interesting way to use custom element slots In this case, the img slot=icon> will be slotted into the named slot slot name