const arr = [1, 2, 1, 2, 1, 2, 1, 2, 1];
const [_, ans] = arr.reduce((acc, y) => {
const [x, a, up, down] = acc;
const cup = x < y || up;
const cdown = x > y || down;
if (cup && cdown) {
return [y, a + 1, false, false];
} else {
return [y, a, cup, cdown];
}
}, [arr[0], 0, false, false]);
console.log(ans + 1);