The before() method of the CharacterData interface inserts a set of Node objects and strings in the children list of the CharacterData's parent, just before the CharacterData node.

Strings are inserted as Text nodes; the string is being passed as argument to the Text() constructor.

nodes

A set of Node or strings to insert.

HierarchyRequestError DOMException

Thrown when the new nodes cannot be inserted at the specified point in the hierarchy, that is if one of the following conditions is met:

• If the insertion of one of the added node would lead to a cycle, that is if one of them is an ancestor of this CharacterData node.
• If one of the added node is not a DocumentFragment, a DocumentType, an Element, or a CharacterData.
• If this CharacterData node is actually a Text node, and its parent is a Document.
• If the parent of this CharacterData node is a Document and one of the nodes to insert is a DocumentFragment with more than one Element child, or that has a Text child.

The before() method allows you to insert new nodes before a CharacterData node leaving the current node's data unchanged.

const h1TextNode = document.querySelector("h1").firstChild;
h1TextNode.before("h1# ");

h1TextNode.parentElement.childNodes;
// NodeList [#text "h1# ", #text "CharacterData.before()"]

h1TextNode.data;
// "CharacterData.before()"

• CharacterData.appendData()
• CharacterData.after()
• Element.append()
• Node.appendChild()
• Element.insertAdjacentElement()