// Advanced utilities (runtime illustration) const numbers = [1, 2, 3, "a", "b"]; const justNumbers = numbers.filter((v) => typeof v === "number"); const justStrings = numbers.filter((v) => typeof v === "string"); console.log(JSON.stringify(justNumbers)); console.log(JSON.stringify(justStrings)); // Omit-like at runtime const A = { a: "x", b: 2, c: true }; const { a, b, ...rest } = A; // keep 'c' console.log(JSON.stringify({ c: rest.c }));