No Sparse Arrays - Denoland

Disallows sparse arrays.

Sparse arrays are arrays that contain empty slots, which later could be handled either as undefined value or skipped by array methods, and this may lead to unexpected behavior:

typescript

[1, , 2].join(); // => '1,,2'
[1, undefined, 2].join(); // => '1,,2'

[1, , 2].flatMap((item) => item); // => [1, 2]
[1, undefined, 2].flatMap((item) => item); // => [1, undefined, 2]

Invalid:

typescript

const items = ["foo", , "bar"];

Valid:

typescript

const items = ["foo", "bar"];