grafana/k6 · error

can't query n-th element in a chained selector with capture

Error message

can't query n-th element in a chained selector with capture

What it means

Mapped from 'error:nthnocapture' by errorFromDOMError (element_handle.go:1896-1916). k6 browser chained selectors (parts joined with '>>') may prefix one part with '*' to capture the element resolved by an intermediate part (selectors.go:44-46). The injected script refuses positional nth= queries inside a chain that uses such a capture, because the n-th index cannot be applied to the captured result.

Source

Thrown at internal/js/modules/k6/browser/common/element_handle.go:1915

		"error:notelement":             "node is not an element",
		"error:nothtmlelement":         "not an HTMLElement",
		"error:notfillableelement":     "element is not an <input>, <textarea> or [contenteditable] element",
		"error:notfillableinputtype":   "input of this type cannot be filled",
		"error:notfillablenumberinput": "cannot type text into input[type=number]",
		"error:notvaliddate":           "malformed value",
		"error:notinput":               "node is not an HTMLInputElement",
		"error:notfile":                "node is not an input[type=file] element",
		"error:hasnovalue":             "node is not an HTMLInputElement or HTMLTextAreaElement or HTMLSelectElement",
		"error:notselect":              "element is not a <select> element",
		"error:notcheckbox":            "not a checkbox or radio button",
		"error:notmultiplefileinput":   "non-multiple file input can only accept single file",
		"error:strictmodeviolation":    "strict mode violation, multiple elements returned for selector query",
		"error:notqueryablenode":       "node is not queryable",
		"error:nthnocapture":           "can't query n-th element in a chained selector with capture",
		"error:intercept":              "another element is intercepting with pointer action",
	}
	if err, ok := errs[serr]; ok {
		return errors.New(err)
	}

	return errors.New(serr)
}

View on GitHub (pinned to 01ffac6f24)

Solutions

1. Remove either the '*' capture prefix or the nth= part so the chain has only one of them
2. Split the work: run the chained query to get the captured element, then use $$/nth on the result in a second query
3. Rewrite as two explicit queries: first resolve the container, then index into its matches

Example fix

// before
const el = await page.$('*css=div.item >> nth=1'); // nth with capture

// after
const items = await page.$$('css=div.item');
const el = items[1];

// Reject capture+nth chains before using them
function isSafeSelector(sel) {
  const parts = sel.split('>>');
  const hasCapture = parts.some(p => p.trim().startsWith('*'));
  const hasNth = parts.some(p => /nth\s*=/.test(p));
  return !(hasCapture && hasNth);
}
if (!isSafeSelector(sel)) throw new Error('split capture/nth into two queries');

try {
  await page.$(sel);
} catch (e) {
  if (/chained selector with capture/.test(e.message)) {
    const items = await page.$$(sel.replace(/\s*nth\s*=\s*\d+/, ''));
    return items[1];
  } else throw e;
}

When it happens

Trigger: A selector string combining a '*' capture prefix with an nth= part in the same chain, e.g. page.$('*css=div.item >> nth=1') or similar chains passed to frame.click/page.waitForSelector. Selector parts are split on '>>' by Selector.parse (selectors.go:82+) and the engine rejects this combination.

Common situations: Building selectors programmatically by concatenating fragments; porting Playwright locator chains (locator.nth()) into k6 chained selector strings.

Related errors

• only one of the selectors can capture using * modifier
• Error while parsing selector `${selector}` - unexpected symb
• Error while parsing selector `${selector}`: ${e.message}
• Error while parsing selector `${selector}` - cannot use ${op
• "${attr.name}" does not support "${attr.op}" matcher

AI-assisted analysis of grafana/k6@01ffac6f24 (2026-08-18). Data as JSON: /api/errors/924689166d95ae6b. Report an issue: GitHub.