I am confused what problem this is solving. You say:

Currently there isn’t a way to create an array by pre-setting its length and an optional filling value that is both straightforward and safe.

https://github.com/jfet97/arraymake#motivation

then you follow with describing safe as being able to create a 2 dimensional array by value instead of reference. but that can already be done a few ways:

const d1 = 5;
const d2 = 2;
Array.from({length: d1}, () => []);
Array.from(Array(d1), () => Array(d2));
Array(d1).fill(null).map(() => Array(d2));

https://stackoverflow.com/questions/966225/-/49201210

and while they could be more straightforward, they are all one line. So it seems this is just sugar. I am not totally against that, but if youre going to do sugar, why not just do:

const two_dim = (d1, d2) => {
   return Array.from(Array(d1), () => Array(d2));
};

instead of the 60 lines here:

https://github.com/jfet97/arraymake/blob/master/src/functional.js