parentNodeinsertBeforenewNode

ParentNode.insertBefore(newNode, referenceNode) is a standard DOM method used to insert a node into a parent node’s children, placing newNode immediately before referenceNode.

Syntax and parameters: The method is invoked on a node that will serve as the parent (parentNode). It takes two arguments: newNode, the node to insert; and referenceNode, the existing child before which newNode should be inserted. If referenceNode is null, newNode is appended as the last child.

Behavior and rules: If newNode already has a different parent, it is removed from that parent and inserted into the new location. If referenceNode is not a child of parentNode, a DOM exception is raised (commonly a HierarchyRequestError). If newNode is a DocumentFragment, all of its children are inserted into the parent in order, and the fragment is emptied.

Return value: The method returns the node that was inserted (or, in the case of a DocumentFragment, typically the first node inserted or the fragment’s content as defined by the implementation). Browsers generally return newNode.

Browser compatibility: This method is supported by all major browsers and is part of the standard DOM API.

Common usage: It is often used to reorder elements, insert newly created nodes into a specific position, or move existing nodes within the same parent without creating new nodes. It is also used in conjunction with creating elements, text nodes, or cloning nodes to build or modify the document structure dynamically.