EDWIN, 코드리뷰 부탁드립니다.^^ Array.from 을 활용해 봤습니다.

const solution = (arr) => {
    const resultArr = [
        ...arr, 
        ...arr.map((_,location) => Array.from({length:arr.length}, (_,idx) => arr[idx][location])),
        Array.from({length:arr.length}, (_, idx) => arr[idx][idx]),
        Array.from({length:arr.length}, (_,idx) => arr[arr.length-idx-1][arr.length-idx-1])
    ]

    return Math.max(...resultArr.map(list => list.reduce((pre, cur) => pre+cur, 0)))
}