matrix.js

var matrixExample = [
    [1, 2, 3, 4],
    [4, 5, 6, 5],
    [7, 8, 9, 7],
    [7, 8, 9, 7]
]

function sumMatrix(matrix) {
    var arr = []
    var arr2 = []
    matrix.forEach(function(item, i){
        if (i == 0) {
            arr.push(item[0])
            arr2.push(item[3])
        }
        else if (i == 1) {
            arr.push(item[1])
            arr2.push(item[2])
        }
        else if (i == 2) {
            arr.push(item[2])
            arr2.push(item[1])
        }
        else {
            arr.push(item[3])
            arr2.push(item[0])
        }
})

    var general_d = arr.reduce(function(sum, current) {
        return sum + current;
    }, 0)
    var not_general_d = arr2.reduce(function(sum, current) {
        return sum + current
    }, 0)
    
    var sum = general_d + not_general_d
    console.log(sum)
}

sumMatrix(matrixExample);