All you wanted to do with "A1:D5" ranges
Dist folder has a compatible ES-5 code, can be used from both back-, and front-end.
function test_ranger() {
const ranger = new Ranger_("A1:B25");
const grid = ranger.grid();
if (!grid) {
console.log(ranger.validation().message);
} else {
console.log(JSON.stringify(grid, null, 2));
}
}