sortarraybylastname.js

function sortArray(values) {
  return values.sort(function (a, b) {
    let authorChuckedA = a.author.split(" ");
    let authorChuckedB = b.author.split(" ");
    let lastNameA = authorChuckedA[authorChuckedA.length - 1];
    let lastNameB = authorChuckedB[authorChuckedB.length - 1];

    return lastNameA.localeCompare(lastNameB);
  });
}

let sorted = sortArray([
  { name: "Harry Potter", rating: "8+", author: "Joanne Rowling" },
  { name: "Warcross", rating: "13+", author: "Marie Lu" },
  { name: "The Hunger Games", rating: "12+", author: "Suzanne Collins" },
]);

console.log(sorted);