Text Between Nodes

Requirements

• Export getTextBetweenNodes(root, start, end) as named and default. All arguments are DOM Nodes. root must contain both boundaries (root itself is allowed). Throw TypeError if either boundary lies outside that root.
• Traverse root and its descendants in preorder: visit a node before its children, and visit siblings from left to right. Return the concatenated nodeValue of Text nodes strictly after start and strictly before end in this traversal.
• Exclude a Text boundary’s own contents. If start is an Element, its descendants come after it and can contribute text; end and all descendants reached after it are excluded. Identical boundaries return an empty string. Reversed boundaries throw RangeError.
• Preserve whitespace and entities as represented in Text nodes; add no separators. Ignore Comment nodes and other non-Text nodes themselves. Text inside script/style or hidden elements is included if it falls in the interval; this is text traversal, not rendered-text extraction.
• Support connected or detached trees, DocumentFragment roots, nested elements, adjacent text nodes, and empty intervals. Do not mutate the DOM or rely on layout, selection, CSS, innerText, or innerHTML parsing.
• Implement traversal yourself. Tests create the fixture DOM programmatically, so no HTML or CSS file needs to be authored. Cross-document/shadow-DOM traversal and character offsets inside boundary nodes are outside scope.

Examples

Input: // root: <div><i id="start">one</i><b>two</b><i id="end">three</i></div>
getTextBetweenNodes(root, start, end);
Output: "onetwo" because the start element’s text is after the start node.

Input: // root child nodes: Text("A"), Text("B"), Text("C")
getTextBetweenNodes(root, root.firstChild, root.lastChild);
Output: "B"