LV1 :: 행렬의 덧셈

https://school.programmers.co.kr/learn/courses/30/lessons/12950

프로그래머스

function solution(arr1, arr2) {
    var result = [];
    let arr = []; 
    for (i = 0; i < arr1.length; i++) {
        arr = [];
        for (j = 0; j < arr1[i].length; j++) { 
            arr.push(arr1[i][j] + arr2[i][j]);
        }
        result.push(arr);
    }
    return result;
}