grafana/k6 · error · InvalidSelectorError

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

Error message

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

What it means

Thrown as a GoError JavaScript exception by Selection.varargFnCall (js/modules/k6/html/html.go:93) when the selector argument passed to an HTML Selection method is not one of the supported types. The dispatch accepts a Selection, a string, an Element, or a sobek.Value (which is unwrapped and re-dispatched); every other Go type falls through to the default branch and panics via rt.NewGoError. This guards the jQuery-style methods Add, Find, Closest, Has and Not, which forward to goquery's string/Selection/node filter functions.

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();

View on GitHub (pinned to 93accf6570)

Solutions

1. Pass a CSS selector string: `doc.find('.item')`
2. To search within a previous result, pass another Selection: `doc.find(items)`
3. To use a node, pass an Element: `doc.find(doc.find('h1').get(0))`
4. Check dynamic inputs before use: `if (typeof sel === 'string') doc.find(sel);`
5. Wrap the call in try/catch on GoError if the selector is user-supplied at runtime

Example fix

// before
const locator = options.selector; // undefined because options lacks 'selector'
doc.find(locator); // GoError: cannot use a '<nil>' as a selector

// after
const locator = options.selector;
if (typeof locator === 'string') {
  doc.find(locator);
}

const isSelectorArg = (a) =>
  typeof a === 'string' ||
  (a !== null && typeof a === 'object' && typeof a.find === 'function' && typeof a.add === 'function');

function safeFind(sel, arg) {
  if (!isSelectorArg(arg)) throw new Error(`invalid selector: ${typeof arg}`);
  return sel.find(arg);
}

function isSelector(a) {
  if (typeof a === 'string') return true; // CSS selector
  if (a && typeof a === 'object' && typeof a.find === 'function') return true; // Selection
  if (a && typeof a === 'object' && a.nodeType === 1) return true; // Element (ok for add/find/closest/has)
  return false;
}

try {
  doc.find(arg);
} catch (e) {
  if (/cannot use a '.*' as a selector/.test(String(e.message))) {
    // bad dynamic input: log and fall back to a default selector
    doc.find('.fallback');
  } else {
    throw e;
  }
}

When it happens

Trigger: Calling `sel.add(arg)`, `sel.find(arg)`, `sel.closest(arg)`, `sel.has(arg)` or `sel.not(arg)` on a Selection returned by parseHTML() where arg is a number, boolean, plain object, array, null or undefined (nil exports also land in the default case and print '<nil>' for %T). Typical case: passing a DOM property or a variable that is undefined, e.g. `doc.find(locator)` where locator came from an options object that lacks the key.

Common situations: Dynamic selectors sourced from __ENV or options that are undefined; confusing k6's Element (returned by sel.get(0), which IS accepted here) with a plain JS object; passing an array of selectors expecting multi-select; refactoring jQuery code that tolerated odd arguments.

Related errors

• Error while parsing selector `${selector}` - cannot use ${op
• Unexpected end of selector while parsing selector `${selecto
• the argument to each() must be a function
• the argument to filter() must be a function, a selector or a
• the argument to is() must be a function, a selector or a sel

AI-assisted analysis of grafana/k6@93accf6570 (2026-08-15). Data as JSON: /api/errors/dddd2884916807e4. Report an issue: GitHub.