The Node.lastChild read-only property returns the last child of the node. If its parent is an element, then the child is generally an element node, a text node, or a comment node. It returns null if there are no child elements.
var last_child = element.lastChild
var tr = document.getElementById("row1");
var corner_td = tr.lastChild;
NodeAttrByteStringCDATASectionCharacterDataChildNodeCommentCustomEventDOMConfigurationDOMErrorDOMErrorHandlerDOMExceptionDOMImplementationDOMImplementationListDOMImplementationRegistryDOMImplementationSourceDOMLocatorDOMObjectDOMParserDOMPointDOMRectDOMStringDOMTimeStampDOMTokenListDOMUserDataDocumentDocumentFragmentDocumentTypeElementElementTraversalEntityEntityReferenceEventEventTargetHTMLCollectionMutationObserverNodeFilterNodeIteratorNodeListNonDocumentTypeChildNodeProcessingInstructionPromiseResolverRangeTextTextDecoderTextEncoderTimeRangesTreeWalkerTypeInfoUSVStringUserDataHandlerXMLDocument