the best way to do it is
const object = Object.keys(o).sort().reduce((r, k) => (r[k] = o[k], r), {})
//else if its in reverse just do
const object = Object.keys(0).reverse ()
You can first convert your almost-array-like object to a real array, and then use .reverse():
Object.assign([], {1:'banana', 2:'apple',
3:'orange'}).reverse();
// [ "orange", "apple", "banana", <1 empty slot> ]
The empty slot at the end if cause because your first index is 1 instead of 0. You can remove the empty slot with .length-- or .pop().
Alternatively, if you want to borrow .reverse and call it on the same object, it must be a fully-array-like object. That is, it needs a length property:
Array.prototype.reverse.call({1:'banana', 2:'apple',
3:'orange', length:4});
// {0:"orange", 1:"apple", 3:"banana", length:4}
Note it will return the same fully-array-like object object, so it won't be a real array. You can then use delete to remove the length property.