Can't handle sparse array correctly

[CrescentSine]

case:
format([,3.14,6,,98])
result:
"return {\n\n 3.14,\n 6,\n\n 98,\n}"
should be:
"return {\n nil,\n 3.14,\n 6,\n nil,\n 98,\n}"

[m-imperfect]

JSON syntax doesn't really support sparse array.
I think this package is designed to format JSON arrays not JS,
but anyway, it's easy to replace the empty slots in a sparse array, for example:

let sparseArray = [,3.14,6,,98]
console.log([...sparseArray]) // [undefined, 3.14, 6, undefined, 98]

also, it's possible to do:

let sparseArray = [,3.14,6,,98]
let array = ([...sparseArray]).map(value => value === undefined ? null : value)
console.log(array) // [null, 3.14, 6, null, 98]

in order to avoid undefined values.

I think this should be left for the user to replace those empty slots, as JSON won't have them in anyway.