fx

fx queries JSON with plain JavaScript — .filter, .map and ordinary property access, the methods you already know, instead of another expression language to learn. Given no expression at all, it opens a full-screen viewer instead.

The demo has a page of the GitHub API sitting on disk. Run fx repos.json '.length', then '.map(r => r.name)', then a filter chained onto a map. fx deploy.json with no expression opens the viewer, where Enter folds and unfolds the line under the cursor and / searches. The VM is private to your browser tab; nothing you type leaves it.