grafana/k6 · error · InvalidSelectorError

Error while parsing selector

Error message

Error while parsing selector `${selector}`: ${e.message}

What it means

Frame.Focus() (frame.go:961) wraps failures of the internal focus action with 'focusing %q'. The action resolves the first element matching the selector in the attached state within Timeout and calls ElementHandle.focus (scrollIntoView + DOM focus). Timeouts waiting for the element, strict-mode violations, and evaluation/context errors during the focus call all bubble up inside this message.

Solutions

Confirm the selector matches: const h = await page.waitForSelector(sel, { timeout: 5000 }); then focus.
Use a unique, stable selector (data-testid) and enable Strict only when uniqueness is guaranteed.
Increase the per-call timeout: page.focus(sel, { timeout: 60000 }).
If a previous step (opening a menu, switching a tab) may have failed, assert on it before focusing.

Example fix

// before
await page.focus('#search');

// after
await page.waitForSelector('#search', { state: 'attached', timeout: 10000 });
await page.focus('#search');

Defensive patterns

Strategy: try-catch

Validate before calling

const ok = await page.waitForSelector('#search', { state: 'attached', timeout: 5000 });
if (!ok) throw new Error('search box not present');

Try / catch

try {
  await page.focus('#search', { timeout: 10000 });
} catch (e) {
  if (String(e).startsWith('focusing')) {
    // element missing or frame churn; wait and retry once
    await page.waitForLoadState('domcontentloaded');
    await page.focus('#search', { timeout: 10000 });
  } else throw e;
}

Prevention

Verify prerequisite UI steps (menu open, tab switch) succeeded before focusing their children.
Use unique selectors to avoid strict-mode failures.
Re-acquire frames after any step that can navigate.

When it happens

Trigger: No element matches the selector before opts.Timeout expires; strict mode on and multiple matches; element exists inside a frame that navigates or detaches during the action; the element handle's focus evaluation fails because the execution context was destroyed.

Common situations: Focusing controls that are lazily rendered (modals, dropdowns opened by prior steps that failed silently); typos or stale selectors after UI redesigns; iframes whose content reloads while the script focuses inside them.

Related errors

AI-assisted analysis of grafana/k6@3fcf5388d7 (2026-08-18). Data as JSON: /api/errors/dddd2884916807e4. Report an issue: GitHub.

Appendix: source

Thrown at internal/js/modules/k6/browser/common/js/injected_script.js:1047

          syntaxError("parsing regular expression");
      } else if (inClass && next() === "]") {
        inClass = false;
      } else if (!inClass && next() === "[") {
        inClass = true;
      } else if (!inClass && next() === "/") {
        break;
      }
      source += eat1();
    }
    if (eat1() !== "/")
      syntaxError("parsing regular expression");
    let flags = "";
    while (!EOL && next().match(/[dgimsuy]/))
      flags += eat1();
    try {
      return new RegExp(source, flags);
    } catch (e) {
      throw new InvalidSelectorError(`Error while parsing selector \`${selector}\`: ${e.message}`);
    }
  }
  function readAttributeToken() {
    let token = "";
    skipSpaces();
    if (next() === `'` || next() === `"`)
      token = readQuotedString(next()).slice(1, -1);
    else
      token = readIdentifier();
    if (!token)
      syntaxError("parsing property path");
    return token;
  }
  function readOperator() {
    skipSpaces();
    let op = "";
    if (!EOL)
      op += eat1();

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