Debug with the console

When a request or script does not behave as expected, Fetchpier gives you a few places to look.

Log from scripts

Use fp.log, fp.warn, and fp.error (or console.log/warn/error) in either script phase. Output appears in the scripts console of the response viewer. Logged values are deep-cloned to a safe representation, so you can log whole objects without leaking live references or freezing on a circular graph.

const body = fp.response.json();
fp.log('response body', body);
fp.warn('status', fp.response.status);

Check the Tests tab

Assertions registered with fp.test show up in the Tests tab as pass/fail, with the error message for failures. See Tests and assertions.

fp.test('status is 200', () => fp.expect(fp.response.status).to.equal(200));

Watch for unresolved variables

If a {{variable}} is not defined, Fetchpier leaves it literal and flags it in the UI, but still sends the request — so you can see exactly what went out. Check the resolved request in the activity record to confirm what was actually sent.

Lean on the script editor

The pre/post script editors flag type errors, unused identifiers, and deprecated fp.* members inline, and they will not autocomplete anything the sandbox would reject (no Promise, no setTimeout, no DOM). If a completion does not appear, the sandbox does not support it.