The after() method of the CharacterData interface inserts a set of Node objects or strings in the children list of the object's parent, just after the object itself.
Strings are inserted as Text nodes; the string is being passed as argument to the Text() constructor.
The after() method allows you to insert new nodes after a CharacterData node.
const h1TextNode = document.querySelector("h1").firstChild;
h1TextNode.after(" #h1");
h1TextNode.parentElement.childNodes;
h1TextNode.data;
Note: If you rather want to append text to the current node, the appendData() method lets you append to the current node's data.