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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);