map - reduce in javascript

map-reduce.ts

class Something {
  foo: string;
  bar: string;
  x: number;
  constructor(x: number) {
    this.x = x;
    this.foo = 'foo';
    this.bar = 'bar';
  }
}

const objects = [new Something(0), new Something(1), new Something(2)];
const xOfObjects = objects.map(function(object) {
  return object.x;
});

console.log(xOfObjects);

const sumOfXs = objects
  .map(obj => obj.x)
  .reduce(function(sum, nextItem) {
    return sum + nextItem;
  }, 0);
console.log(sumOfXs);