const people = [
  { firstName: "Aaron", lastName: "Smith" },
  { firstName: "Émile", lastName: "Zola" },
  { firstName: "Charlotte", lastName: "Brown" },
  { firstName: "Beyoncé", lastName: "Knowles" },
  { firstName: "Ólafur", lastName: "Arnalds" },
  { firstName: "David", lastName: "Jones" },
  { firstName: "Zoë", lastName: "Deschanel" },
];

function sortAlphabetically(arr) {
  return arr.sort((a, b) => {
    if (a.firstName < b.firstName) {
      return -1;
    }

    if (a.firstName > b.firstName) {
      return 1;
    }

    return 0;
  });
}

sortAlphabetically(people);

By default, string comparison in JavaScript is not language-sensitive (meaning it doesn’t take into account language-specific rules or special characters like accents), which results in the sorted list not being in the correct order.

The solution is to leverage Intl.Collator which enables language-sensitive string comparison.

function sortAlphabetically(arr) {
  const collator = new Intl.Collator("en", { sensitivity: "base" });
  return arr.sort((a, b) => collator.compare(a.firstName, b.firstName));
}