Unlike older formats (microdata, RDFa) that weave attributes into HTML tags, JSON-LD lives in one self-contained block, which makes it easy to generate from the same data that renders the page — the safest way to guarantee markup and visible content never drift apart.
A page can carry multiple JSON-LD blocks (Organization + Article + FAQPage is a common trio). Validate with Google's Rich Results Test or an automated checker after every template change.