how to shift left an array "o(1)" code example

Example: rorate array

function rotateArray(A, K) {
    if (!A.length) return A;
    let index = -1;
    while (++index < K) {
        A.unshift(A.pop());
    }
    return A;
}

[
    rotateArray([3, 8, 9, 7, 6], 3),
    rotateArray([0, 0, 0], 1),
    rotateArray([1, 2, 3, 4], 4),
    rotateArray([], 4),
].join(' | ');