<template>: The Content Template element
The <template> HTML element serves as a mechanism for holding HTML fragments, which can either be used later via JavaScript or generated immediately into shadow DOM. This feature is well established and works across many devices and browser versions. It’s been available across browsers since November 2015. Attributes This element includes the global attributes. shadowrootmode Creates a shadow root for the parent element. It is a declarative version of the Element.attachShadow() method and ac