code: function splitSelector (sel, splitter, inBracket) {
    if (sel.indexOf(splitter) < 0) return [sel]
    for (var c, i = 0, n = 0, instr = '', prev = 0, d = []; c = sel.charAt(i); i++) {
      if (instr) {
        if (c == instr && sel.charAt(i-1)!='\\') instr = '';
        continue
      }
      if (c == '"' || c == '\'') instr = c;
      /* istanbul ignore if  */
      if(!inBracket){
        if (c == '(' || c == '[') n++;
        if (c == ')' || c == ']') n--;
      }
      if (!n && c == splitter) d.push(sel.substring(prev, i)), prev = i + 1;
    }
    return d.concat(sel.substring(prev))
  }
docs: split selector with splitter, aware of css attributes