Function Sizzle

e2e/samples/app/slate/source/javascripts/lib/_jquery.js:730–856

(selector, context, results, seed)

      }

      function Sizzle(selector, context, results, seed) {
        var m,
          i,
          elem,
          nid,
          match,
          groups,
          newSelector,
          newContext = context && context.ownerDocument,
          // nodeType defaults to 9, since context defaults to document
          nodeType = context ? context.nodeType : 9;

        results = results || [];

        // Return early from calls with invalid selector or context
        if (typeof selector !== "string" || !selector || (nodeType !== 1 && nodeType !== 9 && nodeType !== 11)) {
          return results;
        }

        // Try to shortcut find operations (as opposed to filters) in HTML documents
        if (!seed) {
          setDocument(context);
          context = context || document;

          if (documentIsHTML) {
            // If the selector is sufficiently simple, try using a "get*By*" DOM method
            // (excepting DocumentFragment context, where the methods don't exist)
            if (nodeType !== 11 && (match = rquickExpr.exec(selector))) {
              // ID selector
              if ((m = match[1])) {
                // Document context
                if (nodeType === 9) {
                  if ((elem = context.getElementById(m))) {
                    // Support: IE, Opera, Webkit
                    // TODO: identify versions
                    // getElementById can match elements by name instead of ID
                    if (elem.id === m) {
                      results.push(elem);
                      return results;
                    }
                  } else {
                    return results;
                  }

                  // Element context
                } else {
                  // Support: IE, Opera, Webkit
                  // TODO: identify versions
                  // getElementById can match elements by name instead of ID
                  if (newContext && (elem = newContext.getElementById(m)) && contains(context, elem) && elem.id === m) {
                    results.push(elem);
                    return results;
                  }
                }

                // Type selector
              } else if (match[2]) {
                push.apply(results, context.getElementsByTagName(selector));