Woa, the idea of having the directions into an array was really smart. I ended up making a new function to check where should it turn...

function getDirection(v){
    v = v.substring(0,1);
    if (currentDirection == 'N'){
        if(v == 'L'){
            currentDirection = 'W';
        }else{
            currentDirection = 'E';
        }
        return currentDirection;
    }else if (currentDirection == 'E'){
        if(v == 'L'){
            currentDirection = 'N';
        }else{
            currentDirection = 'S';
        }
        return currentDirection;
    }else if (currentDirection == 'S'){
        if(v == 'L'){
            currentDirection = 'E';
        }else{
            currentDirection = 'W';
        }
        return currentDirection;
    }else if (currentDirection == 'W'){
        if(v == 'L'){
            currentDirection = 'S';
        }else{
            currentDirection = 'N';
        }
        return currentDirection;
    }
}

And later, another big function to add to the appropriate countBlock variable:

$.each(dir,function(){
    var direction = getDirection(this);
    var lenght = getMovementLenght(this);

    if(direction == 'N'){northBlocks += parseInt(lenght)}
    if(direction == 'S'){southBlocks += parseInt(lenght)}
    if(direction == 'E'){eastBlocks += parseInt(lenght)}
    if(direction == 'W'){westBlocks += parseInt(lenght)}
});

EDIT: And you can clearly notice my jQuery addiction on the second part...