Detailed answer
Template holds inert markup for later instantiation.
JavaScript can clone its content and insert the result into the document. This separates a reusable structure from its instances. Keep cloned IDs unique and use safe text insertion for user values. A template is not an automatic loop or rendering framework.
Example
<template id="card"><article><h2>HTML example</h2></article></template>
<script>document.body.append(document.querySelector("#card").content.cloneNode(true));</script>
Understanding the behavior
Template stores a fragment that is not rendered as normal document content until code clones or inserts it. Its content is available through the template's content DocumentFragment. Repeated clones still need distinct IDs when they contain labeled controls or fragment targets.
Practical implementation notes
Clone the fragment, append it to a visible container and inspect the resulting elements. If the template contains dynamic user text, insert that text safely instead of constructing unsanitized HTML strings.
How to check it
Clone template.content and append the clone, then check repeated instances for duplicate IDs.
Expected result
Only inserted clones become ordinary rendered content.
Watch out: Repeated cloning can introduce duplicate IDs.
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