Get the differences between two XML structures: https://stackoverflow.com/questions/60481648/algorithm-js-or-pseudocode-to-get-difference-between-two-xml-trees

xml-diff.js

const xml = require('xml-parse');

// recursive function to build map
function buildMap(element, path, map) {
  map[path] = {}
  // const childElements = element.childNodes.filter(childNode => childNode.type === 'element');
  for (const childNode of element.childNodes) {
    // skip text (because the xml-parse package also returns the unnecessary texts in an XML structure, e.g. line breaks)
    if (childNode.type === 'text') continue;

    // process child element  
    // add child element's name to indicate that this path has a child with this name
    // use child element's type (dir/file) as the value
    map[path][childNode.attributes.name] = childNode.tagName;

    // if child element is dir, process it recursively
    if (childNode.tagName === 'dir') buildMap(childNode, `${path}/${childNode.attributes.name}`, map);
  }
}

// function to get the differences between two maps
function diffMaps(oldMap, newMap) {
  const changes = [];
  // traverse each path of the old map
  for (const key of Object.keys(oldMap)) {
    // get children in this path for both old map and new map
    const oldChildren = oldMap[key];
    const newChildren = newMap[key];
    changes.push(...diffChildren(key, oldChildren, newChildren));
  }
  return changes;
}

// function to get the differences between the children of two maps
function diffChildren(path, oldChildren, newChildren) {
  const changes = [];
  // traverse each child of the old children
  for (const key of Object.keys(oldChildren)) {
    // if new children also have that child ==> no change ==> remove that child from new children and continue
    if (newChildren[key]) {
      // the reason for deleting is that after we have deleted all the keys that are present in old children, the remaining keys in new children will be the newly added ones.
      delete newChildren[key];
      continue;
    }

    // new children don't have that child ==> deleted ==> add to changes
    const type = oldChildren[key];
    changes.push({
      node: type === 'dir' ? `<dir name="${key}">` : `<file name="${key}"/>`,
      path: path,
      change: 'deleted'
    });
  }

  // traverse each child of the new children and add them to changes
  for (const key of Object.keys(newChildren)) {
    const type = newChildren[key];
    changes.push({
      node: type === 'dir' ? `<dir name="${key}">` : `<file name="${key}"/>`,
      path: path,
      change: 'added'
    });
  }

  return changes;
}

// testing
const oldXmlString = String.raw`
<dir name="rootDir">
    <dir name="childDir">
        <file name="hello.jpg"/>
    </dir>
    <file name="linux.txt"/>
    <file name="img.png"/>
</dir>
`.trim();

const newXmlString = String.raw`
<dir name="rootDir">
    <dir name="childDir">
        <file name="hello.jpg"/>
        <file name="interesting.brain"/>
    </dir>
    <dir name="photos">
        <file name="me.dng"/>
    </dir>
    <file name="img.png"/>
</dir>
`.trim();

const oldXml = xml.parse(oldXmlString);
const newXml = xml.parse(newXmlString);

const oldRoot = oldXml[0];
const newRoot = newXml[0];

const oldMap = {};
const newMap = {};

buildMap(oldRoot, `/${oldRoot.attributes.name}`, oldMap);
buildMap(newRoot, `/${newRoot.attributes.name}`, newMap);

const diffs = diffMaps(oldMap, newMap);
console.log(diffs);