Invalid JSON.

Theory. JSON.parse throws a SyntaxError on invalid text — a missing quote, a trailing comma, a cut-off end. If you do not catch it, the script stops and the page stays half done.

The fix is try/catch around parse:

let data = null; try { data = JSON.parse(text); } catch (error) { status.textContent = "bad-json"; }

The error is an expected case, not a panic: the data comes from outside (storage, file, network) and may be damaged. Show a clear state to the user — do not stay silent and do not show half-read data.

A small function helps: parseOrNull(text) returns data or null. Then you check for null.

Common mistake: try/catch around more code than needed; an empty catch with no message; putting data into the DOM before it is clear that parse succeeded.