function f1(a, bIs, cIs, dIs, {b}={b: 3}, c=4, [d]=[5]) (
  assertEq(a, 1),
  assertEq(b, bIs),
  assertEq(c, cIs),
  assertEq(d, dIs)
);
assertEq(f1.length, 4);
f1(1, 3, 4, 5);
f1(1, 42, 43, 44, {b: 42}, 43, [44]);

let f2 = (a, bIs, cIs, dIs, {b}={b: 3}, c=4, [d]=[5]) => (
  assertEq(a, 1),
  assertEq(b, bIs),
  assertEq(c, cIs),
  assertEq(d, dIs)
);
assertEq(f2.length, 4);
f2(1, 3, 4, 5);
f2(1, 42, 43, 44, {b: 42}, 43, [44]);