[Matre]

function find(A, B) {
	R = [-1, -1];
	outer: for (var i = 0; i < A.length; i++) {
		for (var j = 0; j < B.length; j++) {
			if (A[i] == B[j]) {
				R = [i, j];
				break outer;
				break;
			}
		}
	}
	return R;
}

(R[0] + 1) * (R[1] + 1) итераций.

function find(A, B) {
	var C = {}, R = [-1, -1];
	for (var i = A.length - 1; i >= 0; i--)
		C[A[i]] = i;
	for (var i = 0; i < B.length; i++) {
		if (B[i] in C) {
			R = [C[B[i]], i];
			break;
		}
	}
	return R;
}

A.length + R[1] - 1 итераций.