test1.js

let data = [4,9,13,102,103,101,25,22,21,20,18,9,1]

function min(data) {
    return Math.min(data[0], data[data.length-1])
}

function max(data, index) {
    index = !index ? Math.floor(data.length / 2) : index

    let left = data[index-1]
    let right = data[index+1]

    let current = data[index]

    if (current > left && current > right) {
        return current
    }

    if (left > right) {
        return max(data, index - Math.floor(index / 2))
    } else {
        return max(data, index + Math.floor(index / 2))
    }
}

console.log(max(data))