• Want to help us with this year's BoS Trials?
    Let us know before 30 June. See this thread for details
  • Looking for HSC notes and resources?
    Check out our Notes & Resources page

Snakes Game in JavaScript (1 Viewer)

Ramindu

New Member
Joined
Aug 19, 2013
Messages
6
Gender
Male
HSC
N/A
This is the snake game written using Javascript. I've tried to write it in Object oriented form as much as possible. The logic is that basically, the snake is a composition of nodes, where the starting node is the only node which moves by itself. Every other node behind it occupies the node which is next to it.
The list is basically an array of nodes which eventually, is the snake.
This program could be made more extensive by making the list as an object as well. That could mean that we could have mutiple snakes, but then the keyboard operations to that will also have to change.
This was relating to the logic. All the nodes and the balls were drawn in HTML canvas.
And here is its code

<!doctype html>

<html lang="en">
<head>
<meta charset="UTF-8">
<title>Simple Snake Game</title>

<!-- Basic styling, centering of the canvas. -->
<style>
canvas {
display: block;
position: absolute;
border: 1px solid #000;
margin: auto;
top: 0;
bottom: 0;
right: 0;
left: 0;
}
</style>
</head>
<body>
<script>
var

/**
* Constats
*/
COLS = 26,
ROWS = 26,

EMPTY = 0,
SNAKE = 1,
FRUIT = 2,

LEFT = 0,
UP = 1,
RIGHT = 2,
DOWN = 3,

KEY_LEFT = 37,
KEY_UP = 38,
KEY_RIGHT = 39,
KEY_DOWN = 40,


/**
* Game objects
*/
canvas, /* HTMLCanvas */
ctx, /* CanvasRenderingContext2d */
keystate, /* Object, used for keyboard inputs */
frames, /* number, used for animation */
score; /* number, keep track of the player score */


/**
* Grid datastructor, usefull in games where the game world is
* confined in absolute sized chunks of data or information.
*
* @type {Object}
*/
grid = {

width: null, /* number, the number of columns */
height: null, /* number, the number of rows */
_grid: null, /* Array<any>, data representation */

/**
* Initiate and fill a c x r grid with the value of d
* @param {any} d default value to fill with
* @param {number} c number of columns
* @param {number} r number of rows
*/
init: function(d, c, r) {
this.width = c;
this.height = r;

this._grid = [];
for (var x=0; x < c; x++) {
this._grid.push([]);
for (var y=0; y < r; y++) {
this._grid[x].push(d);
}
}
},

/**
* Set the value of the grid cell at (x, y)
*
* @param {any} val what to set
* @param {number} x the x-coordinate
* @param {number} y the y-coordinate
*/
set: function(val, x, y) {
this._grid[x][y] = val;
},

/**
* Get the value of the cell at (x, y)
*
* @param {number} x the x-coordinate
* @param {number} y the y-coordinate
* @return {any} the value at the cell
*/
get: function(x, y) {
return this._grid[x][y];
}
}

/**
* The snake, works as a queue (FIFO, first in first out) of data
* with all the current positions in the grid with the snake id
*
* @type {Object}
*/
snake = {

direction: null, /* number, the direction */
last: null, /* Object, pointer to the last element in
the queue */
_queue: null, /* Array<number>, data representation*/

/**
* Clears the queue and sets the start position and direction
*
* @param {number} d start direction
* @param {number} x start x-coordinate
* @param {number} y start y-coordinate
*/
init: function(d, x, y) {
this.direction = d;

this._queue = [];
this.insert(x, y);
},

/**
* Adds an element to the queue
*
* @param {number} x x-coordinate
* @param {number} y y-coordinate
*/
insert: function(x, y) {
// unshift prepends an element to an array
this._queue.unshift({x:x, y:y});
this.last = this._queue[0];
},

/**
* Removes and returns the first element in the queue.
*
* @return {Object} the first element
*/
remove: function() {
// pop returns the last element of an array
return this._queue.pop();
}
};

/**
* Set a food id at a random free cell in the grid
*/
function setFood() {
var empty = [];
// iterate through the grid and find all empty cells
for (var x=0; x < grid.width; x++) {
for (var y=0; y < grid.height; y++) {
if (grid.get(x, y) === EMPTY) {
empty.push({x:x, y:y});
}
}
}
// chooses a random cell
var randpos = empty[Math.round(Math.random()*(empty.length - 1))];
grid.set(FRUIT, randpos.x, randpos.y);
}

/**
* Starts the game
*/
function main() {
// create and initiate the canvas element
canvas = document.createElement("canvas");
canvas.width = COLS*20;
canvas.height = ROWS*20;
ctx = canvas.getContext("2d");
// add the canvas element to the body of the document
document.body.appendChild(canvas);

// sets an base font for bigger score display
ctx.font = "12px Helvetica";

frames = 0;
keystate = {};
// keeps track of the keybourd input
document.addEventListener("keydown", function(evt) {
keystate[evt.keyCode] = true;
});
document.addEventListener("keyup", function(evt) {
delete keystate[evt.keyCode];
});

// intatiate game objects and starts the game loop
init();
loop();
}

/**
* Resets and inits game objects
*/
function init() {
score = 0;

grid.init(EMPTY, COLS, ROWS);

var sp = {x:Math.floor(COLS/2), y:ROWS-1};
snake.init(UP, sp.x, sp.y);
grid.set(SNAKE, sp.x, sp.y);

setFood();
}

/**
* The game loop function, used for game updates and rendering
*/
function loop() {
update();
draw();
// When ready to redraw the canvas call the loop function
// first. Runs about 60 frames a second
window.requestAnimationFrame(loop, canvas);
}

/**
* Updates the game logic
*/
function update() {
frames++;

// changing direction of the snake depending on which keys
// that are pressed
if (keystate[KEY_LEFT] && snake.direction !== RIGHT) {
snake.direction = LEFT;
}
if (keystate[KEY_UP] && snake.direction !== DOWN) {
snake.direction = UP;
}
if (keystate[KEY_RIGHT] && snake.direction !== LEFT) {
snake.direction = RIGHT;
}
if (keystate[KEY_DOWN] && snake.direction !== UP) {
snake.direction = DOWN;
}

// each five frames update the game state.
if (frames%5 === 0) {
// pop the last element from the snake queue i.e. the
// head
var nx = snake.last.x;
var ny = snake.last.y;

// updates the position depending on the snake direction
switch (snake.direction) {
case LEFT:
nx--;
break;
case UP:
ny--;
break;
case RIGHT:
nx++;
break;
case DOWN:
ny++;
break;
}

// checks all gameover conditions
if (0 > nx || nx > grid.width-1 ||
0 > ny || ny > grid.height-1 ||
grid.get(nx, ny) === SNAKE
) {
return init();
}

// check wheter the new position are on the fruit item
if (grid.get(nx, ny) === FRUIT) {
// increment the score and sets a new fruit position
score++;
setFood();
} else {
// take out the first item from the snake queue i.e
// the tail and remove id from grid
var tail = snake.remove();
grid.set(EMPTY, tail.x, tail.y);
}

// add a snake id at the new position and append it to
// the snake queue
grid.set(SNAKE, nx, ny);
snake.insert(nx, ny);
}
}

/**
* Render the grid to the canvas.
*/
function draw() {
// calculate tile-width and -height
var tw = canvas.width/grid.width;
var th = canvas.height/grid.height;
// iterate through the grid and draw all cells
for (var x=0; x < grid.width; x++) {
for (var y=0; y < grid.height; y++) {
// sets the fillstyle depending on the id of
// each cell
switch (grid.get(x, y)) {
case EMPTY:
ctx.fillStyle = "#fff";
break;
case SNAKE:
ctx.fillStyle = "#0ff";
break;
case FRUIT:
ctx.fillStyle = "#f00";
break;
}
ctx.fillRect(x*tw, y*th, tw, th);
}
}
// changes the fillstyle once more and draws the score
// message to the canvas
ctx.fillStyle = "#000";
ctx.fillText("SCORE: " + score, 10, canvas.height-10);
}

// start and run the game
main();
</script>
</body>
</html>
 

Ramindu

New Member
Joined
Aug 19, 2013
Messages
6
Gender
Male
HSC
N/A
<!doctype html>

<html lang="en">
<head>
<meta charset="UTF-8">
<title>Simple Snake Game</title>

<!-- Basic styling, centering of the canvas. -->
<style>
canvas {
display: block;
position: absolute;
border: 1px solid #000;
margin: auto;
top: 0;
bottom: 0;
right: 0;
left: 0;
}
</style>
</head>
<body>
<script>
var

/**
* Constats
*/
COLS = 26,
ROWS = 26,

EMPTY = 0,
SNAKE = 1,
FRUIT = 2,

LEFT = 0,
UP = 1,
RIGHT = 2,
DOWN = 3,

KEY_LEFT = 37,
KEY_UP = 38,
KEY_RIGHT = 39,
KEY_DOWN = 40,


/**
* Game objects
*/
canvas, /* HTMLCanvas */
ctx, /* CanvasRenderingContext2d */
keystate, /* Object, used for keyboard inputs */
frames, /* number, used for animation */
score; /* number, keep track of the player score */


/**
* Grid datastructor, usefull in games where the game world is
* confined in absolute sized chunks of data or information.
*
* @type {Object}
*/
grid = {

width: null, /* number, the number of columns */
height: null, /* number, the number of rows */
_grid: null, /* Array<any>, data representation */

/**
* Initiate and fill a c x r grid with the value of d
* @param {any} d default value to fill with
* @param {number} c number of columns
* @param {number} r number of rows
*/
init: function(d, c, r) {
this.width = c;
this.height = r;

this._grid = [];
for (var x=0; x < c; x++) {
this._grid.push([]);
for (var y=0; y < r; y++) {
this._grid[x].push(d);
}
}
},

/**
* Set the value of the grid cell at (x, y)
*
* @param {any} val what to set
* @param {number} x the x-coordinate
* @param {number} y the y-coordinate
*/
set: function(val, x, y) {
this._grid[x][y] = val;
},

/**
* Get the value of the cell at (x, y)
*
* @param {number} x the x-coordinate
* @param {number} y the y-coordinate
* @return {any} the value at the cell
*/
get: function(x, y) {
return this._grid[x][y];
}
}

/**
* The snake, works as a queue (FIFO, first in first out) of data
* with all the current positions in the grid with the snake id
*
* @type {Object}
*/
snake = {

direction: null, /* number, the direction */
last: null, /* Object, pointer to the last element in
the queue */
_queue: null, /* Array<number>, data representation*/

/**
* Clears the queue and sets the start position and direction
*
* @param {number} d start direction
* @param {number} x start x-coordinate
* @param {number} y start y-coordinate
*/
init: function(d, x, y) {
this.direction = d;

this._queue = [];
this.insert(x, y);
},

/**
* Adds an element to the queue
*
* @param {number} x x-coordinate
* @param {number} y y-coordinate
*/
insert: function(x, y) {
// unshift prepends an element to an array
this._queue.unshift({x:x, y:y});
this.last = this._queue[0];
},

/**
* Removes and returns the first element in the queue.
*
* @return {Object} the first element
*/
remove: function() {
// pop returns the last element of an array
return this._queue.pop();
}
};

/**
* Set a food id at a random free cell in the grid
*/
function setFood() {
var empty = [];
// iterate through the grid and find all empty cells
for (var x=0; x < grid.width; x++) {
for (var y=0; y < grid.height; y++) {
if (grid.get(x, y) === EMPTY) {
empty.push({x:x, y:y});
}
}
}
// chooses a random cell
var randpos = empty[Math.round(Math.random()*(empty.length - 1))];
grid.set(FRUIT, randpos.x, randpos.y);
}

/**
* Starts the game
*/
function main() {
// create and initiate the canvas element
canvas = document.createElement("canvas");
canvas.width = COLS*20;
canvas.height = ROWS*20;
ctx = canvas.getContext("2d");
// add the canvas element to the body of the document
document.body.appendChild(canvas);

// sets an base font for bigger score display
ctx.font = "12px Helvetica";

frames = 0;
keystate = {};
// keeps track of the keybourd input
document.addEventListener("keydown", function(evt) {
keystate[evt.keyCode] = true;
});
document.addEventListener("keyup", function(evt) {
delete keystate[evt.keyCode];
});

// intatiate game objects and starts the game loop
init();
loop();
}

/**
* Resets and inits game objects
*/
function init() {
score = 0;

grid.init(EMPTY, COLS, ROWS);

var sp = {x:Math.floor(COLS/2), y:ROWS-1};
snake.init(UP, sp.x, sp.y);
grid.set(SNAKE, sp.x, sp.y);

setFood();
}

/**
* The game loop function, used for game updates and rendering
*/
function loop() {
update();
draw();
// When ready to redraw the canvas call the loop function
// first. Runs about 60 frames a second
window.requestAnimationFrame(loop, canvas);
}

/**
* Updates the game logic
*/
function update() {
frames++;

// changing direction of the snake depending on which keys
// that are pressed
if (keystate[KEY_LEFT] && snake.direction !== RIGHT) {
snake.direction = LEFT;
}
if (keystate[KEY_UP] && snake.direction !== DOWN) {
snake.direction = UP;
}
if (keystate[KEY_RIGHT] && snake.direction !== LEFT) {
snake.direction = RIGHT;
}
if (keystate[KEY_DOWN] && snake.direction !== UP) {
snake.direction = DOWN;
}

// each five frames update the game state.
if (frames%5 === 0) {
// pop the last element from the snake queue i.e. the
// head
var nx = snake.last.x;
var ny = snake.last.y;

// updates the position depending on the snake direction
switch (snake.direction) {
case LEFT:
nx--;
break;
case UP:
ny--;
break;
case RIGHT:
nx++;
break;
case DOWN:
ny++;
break;
}

// checks all gameover conditions
if (0 > nx || nx > grid.width-1 ||
0 > ny || ny > grid.height-1 ||
grid.get(nx, ny) === SNAKE
) {
return init();
}

// check wheter the new position are on the fruit item
if (grid.get(nx, ny) === FRUIT) {
// increment the score and sets a new fruit position
score++;
setFood();
} else {
// take out the first item from the snake queue i.e
// the tail and remove id from grid
var tail = snake.remove();
grid.set(EMPTY, tail.x, tail.y);
}

// add a snake id at the new position and append it to
// the snake queue
grid.set(SNAKE, nx, ny);
snake.insert(nx, ny);
}
}

/**
* Render the grid to the canvas.
*/
function draw() {
// calculate tile-width and -height
var tw = canvas.width/grid.width;
var th = canvas.height/grid.height;
// iterate through the grid and draw all cells
for (var x=0; x < grid.width; x++) {
for (var y=0; y < grid.height; y++) {
// sets the fillstyle depending on the id of
// each cell
switch (grid.get(x, y)) {
case EMPTY:
ctx.fillStyle = "#fff";
break;
case SNAKE:
ctx.fillStyle = "#0ff";
break;
case FRUIT:
ctx.fillStyle = "#f00";
break;
}
ctx.fillRect(x*tw, y*th, tw, th);
}
}
// changes the fillstyle once more and draws the score
// message to the canvas
ctx.fillStyle = "#000";
ctx.fillText("SCORE: " + score, 10, canvas.height-10);
}

// start and run the game
main();
</script>
</body>
</html>
 

Ramindu

New Member
Joined
Aug 19, 2013
Messages
6
Gender
Male
HSC
N/A
Haha thanks :) I used to go to Oxford Uni btw!! And now I work for Google company!!
 
Last edited:

Users Who Are Viewing This Thread (Users: 0, Guests: 1)

Top