Combine Collection Predicates (ARCH3077)

Key typescript.performance.combine-collection-predicates · Severity info · Category performance

Consecutive filter calls each produce an intermediate array; fusing them into a single predicate avoids the unnecessary intermediate allocations.

Incorrect

function eligible(users: User[]): User[] {
  return users
    .filter((u) => u.active)
    .filter((u) => u.age >= 18);
}

Correct

function eligible(users: User[]): User[] {
  return users.filter((u) => u.active && u.age >= 18);
}

Fix

Combine consecutive filters into a single filter call using &&.