gchq/CyberChef · error · OperationError

Invalid jq expression: ${err.message}

Error message

Invalid jq expression: ${err.message}

What it means

Thrown by the Jq operation when the jq-web engine raises an error compiling or evaluating the query. Input is already-parsed JSON (inputType 'JSON'); the failure is in the query itself or a runtime evaluation error, surfaced as err.message from the WASM-backed jq engine.

Source

Thrown at src/core/operations/Jq.mjs:54

                type: "boolean",
                value: false
            },
        ];
    }

    /**
     * @param {JSON} input
     * @param {Object[]} args
     * @returns {string}
     */
    run(input, args) {
        const [query, raw] = args;
        let result;

        try {
            result = jq.json(input, query);
        } catch (err) {
            throw new OperationError(`Invalid jq expression: ${err.message}`);
        }
        if (raw && typeof result === "string") {
            return result;
        } else {
            return JSON.stringify(result);
        }
    }

}

export default Jq;

View on GitHub (pinned to 4290ea7539)

Solutions

1. Test the query with desktop jq against the same input to isolate syntax vs engine limits.
2. Guard against null-iteration: use '?', '//', or 'map(...)' to avoid errors on missing fields.
3. Simplify the query to the smallest failing fragment and rebuild.
4. Confirm the input is the object Jq expects (parsed JSON), not a raw string.

Example fix

// before: null-iteration error
jq.json(data, '.users[].name'); // .users missing
// after: safe access
jq.json(data, '.users // [] | .[].name');

function safeJqQuery(q) {
  if (typeof q !== 'string' || q.length === 0) throw new Error('Empty jq query');
  const pairs = { ')': '(', ']': '[' };
  const stack = [];
  for (const ch of q) {
    if (ch === '(' || ch === '[') stack.push(ch);
    else if (pairs[ch]) { if (stack.pop() !== pairs[ch]) throw new Error('Unbalanced jq query'); }
  }
  if (stack.length) throw new Error('Unbalanced jq query');
  return q;
}

function isBalancedJqQuery(q) {
  try { safeJqQuery(q); return true; } catch { return false; }
}

try {
  return chef.Jq(jsonObj, { query, raw: false });
} catch (e) {
  if (/Invalid jq expression/.test(e.message))
    throw new Error('Test the query with desktop jq; guard null-iteration with // and ?');
  throw e;
}

When it happens

Trigger: Query syntax errors: misplaced pipes '|', bad object construction, invalid indices. Runtime errors during evaluation: iterating over null, dividing by zero, calling an undefined function. Using a jq feature the bundled jq-web build lacks.

Common situations: Translating between jq and JSONPath. Typing a filter against the wrong data shape. jq-web being an older WASM port lagging behind jq's feature set. Heavy queries hitting WASM limits.

Related errors

• Invalid Jsonata Expression: ${err.message}
• Invalid JPath expression: ${err.message}
• Unable to parse JSON to CSV: ${err.toString()}
• Could not encode JSON to MessagePack: ${err}
• Data is not a valid ${Dish.enumLookup(type)}: ${sample}

AI-assisted analysis of gchq/CyberChef@4290ea7539 (2026-08-13). Data as JSON: /api/errors/20459e47aab621f7. Report an issue: GitHub.