/vercel-react-best-practices

Combine Multiple Array Iterations

Multiple .filter() or .map() calls iterate the array multiple times. Combine into one loop.

Incorrect (3 iterations):

const admins = users.filter((u) => u.isAdmin);
const testers = users.filter((u) => u.isTester);
const inactive = users.filter((u) => !u.isActive);

Correct (1 iteration):

const admins: User[] = [];
const testers: User[] = [];
const inactive: User[] = [];

for (const user of users) {
  if (user.isAdmin) admins.push(user);
  if (user.isTester) testers.push(user);
  if (!user.isActive) inactive.push(user);
}