Optional Chaining (?.) - JavaScript MDN

Optional chaining (?.) - JavaScript | MDN

Example 1

const adventurer = {
  name: 'Alice',
  cat: {
    name: 'Dinah'
  }
};

const dogName = adventurer.dog?.name;
console.log(dogName);
// expected output: undefined

console.log(adventurer.someNonExistentMethod?.());
// expected output: undefined

Example 2

This returns: Cannot read includes property of undefined if array has item without frontmatter[keyChoice]

queryFiles = files.filter(file => app.metadataCache.getFileCache(file).frontmatter[keyChoice].includes(queryValue));

This

queryFiles = files.filter(file => app.metadataCache.getFileCache(file).frontmatter[keyChoice]?.includes(queryValue));