Text nodes in the full depth of the sub-tree underneath this
Element into a "normal" form where only markup (e.g., tags, comments, processing instructions, CDATA sections, and entity references) separates
Text nodes, i.e., there are no adjacent
Text nodes. This can be used to ensure that the DOM view of a document is the same as if it were saved and re-loaded, and is useful when operations (such as XPointer lookups) that depend on a particular document tree structure are to be used.