Firefox/Chrome DOM stdlib: create XML document from scratch, including declaration

createxmldoc.js

// example: createXMLDocumentWithDeclaration('http://www.topografix.com/GPX/1/1', 'gpx', null, 'version="1.0" standalone="yes"')

function createXMLDocumentWithDeclaration(namespaceURI, qualifiedNameStr, documentType=null, declarationData='version="1.0"') {
	const document = new Document().implementation.createDocument(namespaceURI, qualifiedNameStr, documentType);
	// https://www.w3.org/TR/xml/#NT-XMLDecl
	document.insertBefore(document.createProcessingInstruction("xml", declarationData), document.firstChild);
	return document;
}