The Document Object Model (DOM) is a cross-platform^[2] and language-independent API that treats an HTML or XML document as a tree structure wherein each node is an object representing a part of the document. The DOM represents a document with a logical tree. Each branch of the tree ends in a node, and each node contains objects. DOM methods allow programmatic access to the tree; with them one can change the structure, style or content of a document.^[2] Nodes can have event handlers (also known as event listeners) attached to them. Once an event is triggered, the event handlers get executed.^[3]