const Arr = [0, 1, 2];
for (var i = Number.MIN_SAFE_INTEGER; i <= Number.MAX_SAFE_INTEGER; i += 1) { ... }
Need to correlate any given i to an appropriate index in Arr, so that
i=-3 => 0
i=-2 => 1
i=-1 => 2
i=0 => 0
i=1 => 1
i=2 => 2
i=3 => 0
i=4 => 1
i=5 => 2
... etc.
This question does not need the array factor. It is about mapping any integer to a limited range.
This you can do with the following transformation:
j = i - Math.floor(i/3)*3
NB: for positive numbers you could use just i % 3, but it does not give the results you desire for negative numbers.
I might recommend to make an index function that takes an array xs, and an index i. Conceptually, what we want to do is wrap i around if it goes out-of-bounds of xs in either direction. The remainder (%) operator is just what we need for the job
const index = (xs, i) =>
i < 0
? xs [0 - (i % xs.length)]
: xs [i % xs.length]
const data =
[ 'a', 'b', 'c' ]
for (let i = -5; i < 6; i++)
console.log (i, index (data, i))
// -5 'c'
// -4 'b'
// -3 'a'
// -2 'c'
// -1 'b'
// 0 'a'
// 1 'b'
// 2 'c'
// 3 'a'
// 4 'b'
// 5 'c'I've found quite a nice solution to this:
function mod(n, m) {
const q = n % m;
return q < 0 ? q + m : q;
}