green theoreom in javascript

index.tsx
function greenTheorem(points) {
  const n = points.length;

  let area = 0;
  for (let i = 0; i < n; i++) {
    const j = (i + 1) % n;
    area += points[i].x * points[j].y - points[j].x * points[i].y;
  }
  area /= 2;

  let cx = 0, cy = 0;
  for (let i = 0; i < n; i++) {
    const j = (i + 1) % n;
    cx += (points[i].x + points[j].x) * (points[i].x * points[j].y - points[j].x * points[i].y);
    cy += (points[i].y + points[j].y) * (points[i].x * points[j].y - points[j].x * points[i].y);
  }
  cx /= (6 * area);
  cy /= (6 * area);

  return { area, centroid: { x: cx, y: cy } };
}
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index.tsx
const points = [
  { x: 0, y: 0 },
  { x: 1, y: 0 },
  { x: 1, y: 1 },
  { x: 0, y: 1 },
];
const result = greenTheorem(points);
console.log(result);
// { area: 1, centroid: { x: 0.5, y: 0.5 } }
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