Battleship code

<!DOCTYPE html>
<html>
<head>
<script>

var BOARD_WIDTH = 10;
var BOARD_HEIGHT = 10;

// Vector2D "class"
function Vector2D(x, y) {
    return { x: x,
             y: y,
             add: function (other) {
                 return new Vector2D(x + other.x, y + other.y)
             },
             toString: function() {
                 return "(" + x + "," + y + ")";
             }
           };
}

// Constants
var HORIZONTAL = Vector2D(1, 0);
var VERTICAL = Vector2D(0, 1);

// Extend Array class with pickRandom method
Array.prototype.pickRandom = function () {
    var idx = Math.floor( Math.random() * this.length );
    return this[idx];
};

// Returns a random orientation
function randomOrientation() {
    return [ HORIZONTAL, VERTICAL ].pickRandom();
}

// Generates random integers
function randomInteger(maximum) {
    return Math.floor( Math.random() * maximum);
}

// Generates random positions
function randomPosition() {
    return Vector2D( randomInteger(BOARD_WIDTH), randomInteger(BOARD_HEIGHT) );
}

// Boatclass
function Boat(position, orientation, length) {
    return { position: position,
             orientation: orientation,
             length: length,
             hits: (function () {
                var result =  [];
                for(var i = 0; i !== length; i++){
                    result.push(0);
                }
                return result;
            })(),

             usedPositions: function() {
                 var result = [];
                 var current = position;
                 for ( var i = 0; i != length; i++ ) {
                     result.push(current);
                     current = current.add(orientation);
                 }
                 return result;
             }
           };
}

// Checks if x is a memeber of the Array
Array.prototype.member = function (x) {
    for(var i = 0; i !== this.length; i++)
    {
        if(x === this[i]){
            return true;
        }
    }
    return false;
}

// Checks sf xs overlaps with the Array
Array.prototype.overlaps = function (xs) {
    for(var i= 0; i !== xs.length; i++)
    {
        if(this.member(xs[i])){
            return true;
        }
    }
    return false;

}

// Generates a random boat with a set length
function generateRandomBoat(size) {
    return Boat(randomPosition(), randomOrientation(), size);
}

// Checks if all elements of xs equal x
function allEquals(xs, x) {
    var all = true;
    for (var i = 0; i != xs.length; i++) {
        if(xs[i] !== x)
            all = false;
    }
    return all;
}

// Generates an Array with random boats
function randomBoats(sizes) {
    var occupiedPositions = [];
    var boats = [];
    sizes = sizes.slice(); // kopieren

    while ( sizes.length > 0 ) {
        var currentSize = sizes.pop();

        var candidate = generateRandomBoat(currentSize);
        var candidateSpaces = candidate.usedPositions();

        if ( candidateSpaces.overlaps(occupiedPositions) ) {
            sizes.push(currentSize);
        }
        else {
            occupiedPositions = occupiedPositions.concat(candidateSpaces);
            boats.push(candidate);
        }

    }

    for(var i = 0; i !== boats.length; i++) {
        document.write(boats[i].usedPositions());
        document.write(" ||| ");
    }
    return boats;
}

// The game itself
function game(){
    inputArray = [4,3,2];
    var boats = randomBoats(inputArray);
    var currentBoat = 0;
    var sunkenBoat = 0;
    var numberOfTurns = 0;
    while(sunkenBoat !== inputArray.length ) {
        var raak= false;
        var target = "(" + prompt("Enter targetcoordinate (x,y)") + ")";
        var targetString = target.replace(/\s+/g, '');
        for(var i = 0; i !== inputArray.length; i++) {
            for(var j = 0; j !== boats[i].usedPositions().length; j++) {
                console.log(targetString)
                if(targetString === boats[i].usedPositions()[j].toString()) {
                    raak = true;
                    boats[i].hits[j] = 1;
                    console.log(boats[i].hits);
                    currentBoat = boats[i];
                }
                else {
                    currentBoat = boats[i];

                }
            }
        }

        console.log(currentBoat.hits);
        console.log(allEquals(currentBoat.hits, 1));

        if(raak)
            alert ("Hit!");

       else
            alert ("Miss!");

        if(allEquals(currentBoat.hits, 1)) {
            alert("Boat with length " + currentBoat.hits.length + " has sunken!");
            sunkenBoat++;
        }
        numberOfTurns++
    }

    alert("You've won! You did it in " + numberOfTurns + " turns.")
}

game();


</script>
</head>
<body>