The reduce() method performs a reducing function (download for you) for each element of the matrix, resulting in a single return value.

reduce.ts

const githubStars = [
  {
    userID: "tecnobert",
    userStars: 88,
  },
  {
    userID: "philipwalton",
    userStars: 36,
  },
  {
    userID: "cytopia",
    userStars: 370,
  },
];

const totalStars = githubStars.reduce((sum, stars) => {
  return sum + stars.userStars;
}, 0);

console.log(totalStars);