The NamedNodeMap interface represents a collection of Attr objects. Objects inside a NamedNodeMap are not in any particular order, unlike NodeList, although they may be accessed by an index as in an array.
The Node.firstChild read-only property returns the node's first child in the tree, or null if the node is childless. If the node is a Document, it returns the first node in the list of its direct children.
The Node.isEqualNode() method tests whether two nodes are equal. Two nodes are equal when they have the same type, defining characteristics (for elements, this would be their ID, number of children, and so forth), its attributes match, and so on. The specific set of data points that much match varies depending on the types of the nodes.
The Node.nextSibling read-only property returns the node immediately following the specified one in its parent's childNodes list, or null if the specified node is the last node in that list.
The Node.parentElement read-only property returns the DOM node's parent Element, or null if the node either has no parent, or its parent isn't a DOM Element.
Returns a node from a NodeList by index. This method doesn't throw exceptions as long as you provide arguments; a value of null is returned if the index is out of range and a TypeError is thrown if no argument is provided.
The PerformanceResourceTiming interface enables retrieving and analyzing detailed network timing data regarding the loading of an application's resources. An application can use the timing metrics to determine, for example, the length of time it takes to fetch a specific resource, such as an XMLHttpRequest, <SVG>, image, or script.