{
  "with a named property": (() => {
    // A named (non-index) property on an array is left out of the rendering
    // entirely.
    const a = [1, 2];
    a.extra = "x";
    return a;
  })(),
}

--

with a named property:
[1,2]
[
  1,
  2
]
[
  1,
  2
]