var current_position = [];
var cursor = 0;

function queens8() {
    for (var j = 0; j <= 7; j++) {
        if (check(cursor, j) == true) {

            cursor++;
            current_position.push(j);

            if (current_position.length == 8) {

                done_positions.push(current_position);

                console.log(current_position);
                //выводит на первой итерации: [0, 4, 7, 5, 2, 6, 1, 3]

            }
            queens8();
        }
    }
    current_position.splice(cursor-1, 1);
    cursor--;
    return;
}

done_positions.push(current_position);

[Array[0], Array[0], Array[0], Array[0], Array[0], Array[0], ...]

done_positions.push([]+current_position);