function ascendingSort(array) {
    return array.sort(function (a, b) {
        return b - a;
    }).reverse();
}

function descendingSort(array) {
    return array.sort(function (a, b) {
        return b - a;
    });
}
// ascending sort for even rows
// descending sort for odd rows

function sortRowsInMatrix(matrix) {
    var currentRow = [];

    for (var i = 0; i < matrix.length; i++) {
        for (var j = 0; j < matrix.length; j++) {
            currentRow.push(matrix[i][j]);
        }
        if (i % 2 === 0) {
            currentRow = ascendingSort(currentRow);
        }
        else {
            currentRow = descendingSort(currentRow);
        }
        for (var j = 0; j < matrix.length; j++) {
            matrix[i][j] = currentRow[j];
        }
        currentRow = [];
    }

    return matrix;
}

var matrix = [[3, 2, 1], [4, 5, 6], [9, 8, 7]];
console.log(sortRowsInMatrix(matrix));