code: function startTagInTableBody(p, token) {
      const tn = token.tagName;
  
      if (tn === $.TR) {
          p.openElements.clearBackToTableBodyContext();
          p._insertElement(token, NS.HTML);
          p.insertionMode = IN_ROW_MODE;
      } else if (tn === $.TH || tn === $.TD) {
          p.openElements.clearBackToTableBodyContext();
          p._insertFakeElement($.TR);
          p.insertionMode = IN_ROW_MODE;
          p._processToken(token);
      } else if (
          tn === $.CAPTION ||
          tn === $.COL ||
          tn === $.COLGROUP ||
          tn === $.TBODY ||
          tn === $.TFOOT ||
          tn === $.THEAD
      ) {
          if (p.openElements.hasTableBodyContextInTableScope()) {
              p.openElements.clearBackToTableBodyContext();
              p.openElements.pop();
              p.insertionMode = IN_TABLE_MODE;
              p._processToken(token);
          }
      } else {
          startTagInTable(p, token);
      }
  }
docs: The "in table body" insertion mode ------------------------------------------------------------------