const arr = [
    [4, 5, 1, 3],
    [13, 27, 18, 26],
    [32, 35, 37, 39],
    [1000, 1001, 857, 1]
]

function getMaxArr(arr) {
    let result = []
    arr.forEach(item => {
        result.push(Math.max(...item))
    })
    return result;
}
console.log(getMaxArr(arr))