Node.appendChild()

The appendChild() method of the Node interface adds a node to the end of the list of children of a specified parent node. If the given child is a reference to an existing node in the document, appendChild() moves it from its current position to the new position (there is no requirement to remove the node from its parent node before appending it to some other node).

This means that a node can't be in two points of the document simultaneously. So if the node already has a parent, the node is first removed, then appended at the new position. The Node.cloneNode() method can be used to make a copy of the node before appending it under the new parent. Copies made with cloneNode are not automatically kept in sync.

If the given child is a DocumentFragment, the entire contents of the DocumentFragment are moved into the child list of the specified parent node.

Chaining does not work, due to appendChild() returning the child element:

let aBlock = document.createElement('block').appendChild( document.createElement('b') );

Sets aBlock to <b></b> only, meaning you cannot chain further actions on block, like performing several chained appendChild.

aChild

The node to append to the given parent node (commonly an element).

A Node that is the appended child (aChild), except when aChild is a DocumentFragment, in which case the empty DocumentFragment is returned.

HierarchyRequestError DOMException

Thrown when the constraints of the DOM tree are violated, that is if one of the following cases occurs:

• If the parent of aChild is not a Document, DocumentFragment, or an Element.
• If the insertion of aChild would lead to a cycle, that is if aChild is an ancestor of the node.
• If aChild is not a DocumentFragment, a DocumentType, an Element, or a CharacterData.
• If the current node is a Text, and its parent is a Document.
• If the current node is a DocumentType and its parent is not a Document, as a doctype should always be a direct descendant of a document.
• If the parent of the node is a Document and aChild is a DocumentFragment with more than one Element child, or that has a Text child.
• If the insertion of aChild would lead to Document with more than one Element as child.

• Node.removeChild()
• Node.replaceChild()
• Node.insertBefore()
• Node.hasChildNodes()
• Element.insertAdjacentElement()
• Element.append()