JavaScript Snake game - javascript

I am having trouble with the moving of the snake elements. I have written a Snake game in C# desktop application but it the same logic doesn't seem to work in JavaScript.
Here is the part that I am having trouble with. Basically I have 4 functions that only moves the head of the Snake (the first element of the array) and I use this code to move the other parts of the body.
for (i = snakeBody.length - 1; i > 0 ; i--) {
context.rect(snakeBody[i].x,snakeBody[i].y,snakeBody[i].w,snakeBody[i].h);
snakeBody[i]=snakeBody[i-1];
}
The problem is that they all clump on top of each other. I can't understand why this doesn't work in JavaScript.
Here is the entire code.
window.onload= function ()
{
var canvas=document.getElementById("canvas");
var context=canvas.getContext("2d");
var canvasWidth=window.innerWidth;
var canvasHeight=window.innerHeight;
canvas.width=canvasWidth;
canvas.height=canvasHeight;
var up=false;
var down=false;
var left=false;
var right=true;
var snake={
x:20,
y:0,
w:20,
h:20
};
var snakeBody=[];
for (i = 0; i < 5; i++) {
snakeBody.push({
x:snake.x ,
y:snake.y ,
w:snake.w,
h:snake.h
});
snake.x +=20;
}
var food={
x:Math.random() * canvasWidth,
y:Math.random() * canvasHeight,
w:2,
h:2
};
function moveUp()
{
snakeBody[0].y -=3;
}
function moveDown()
{
snakeBody[0].y +=3;
}
function moveLeft()
{
snakeBody[0].x -=3;
}
function moveRight()
{
snakeBody[0].x +=3;
}
function draw()
{
context.clearRect(0,0,canvasWidth,canvasHeight);
context.fillStyle="rgba(230,230,230,0.1)";
context.beginPath();
for (i = snakeBody.length - 1; i > 0 ; i--) {
context.rect(snakeBody[i].x,snakeBody[i].y,snakeBody[i].w,snakeBody[i].h);
snakeBody[i]=snakeBody[i-1];
}
//context.rect(food.x,food.y,food.w,food.h);
context.stroke();
context.fill();
directions();
collision();
update();
}
function directions()
{
document.onkeydown = function(e)
{
var event = window.event ? window.event : e;
var keycode = event.keyCode;
if (keycode===37 && right===false) {
left=true;
right=false;
up=false;
down=false;
}
if (keycode===38 && down===false) {
up=true;
down=false;
left=false;
right=false;
}
if (keycode===39 && left===false) {
right=true;
left=false;
up=false;
down=false;
}
if (keycode===40 && up===false) {
down=true;
up=false;
left=false;
right=false;
}
};
}
function update()
{
if (up) {moveUp();}
if (down) {moveDown();}
if (left) {moveLeft();}
if (right) {moveRight();}
}
function collision()
{
for (i = 0; i < snakeBody.length; i++) {
if (snakeBody[i].x >canvasWidth) {
snakeBody[i].x = 0;
}
if (snakeBody[i].x < 0) {
snakeBody[i].x=canvasWidth;
}
if (snakeBody[i].y>canvasHeight) {
snakeBody[i].y=0;
}
if (snakeBody[i].y <0) {
snakeBody[i].y=canvasHeight;
}
}
}
setInterval(draw,40);
};

I believe your issue is that you mean to set the value of snake[i] to snake[i-1] but you're actually setting snake[i] to a reference of snake[i-1]. You're setting all your array to the be the same object. You can fix this by doing
snake[i].x = snake[i-1].x;
snake[i].y = snake[i-1].y;
You'll also encounter another problem as you're only moving the snake by 3 instead of the width of its body segments.

Related

I am having a bug with the enemies and when they reach your character in a small game I made

The bug happens when you shoot and die at the same time, and in the console it pops up as "Uncaught TypeError: Cannot read property 'draw' of undefined. Line 65"
The thing is, the bug started happening when I included the function that kills the player, which starts on line 143, and the thing that breaks it is the single line
enemy = [];
Here's the enemy function
function Enemy(x, y) {
this.x = x;
this.y = y;
this.draw = function() {
noStroke();
fill(255, 0, 0);
rect(this.x, this.y, 20, 20);
}
this.move = function() {
this.x -= movement; }
this.offscreen = function() {
if(this.x < 0) {
return true;
} else {
return false;
}
}
this.contact = function() {
for(let i = 0; i < enemy.length; i++) {
var d = dist(playerx, playery, enemy[i].x, enemy[i].y);
if(d <= 20) {
this.kill();
}
}
}
this.kill = function() {
var prevScore = score;
playerx = width / 10;
playery = height / 2;
alert("You died! your score was: " + prevScore);
fire = [];
enemy = [];
score = 0
}
}
Here's where it says it's getting the type error (which worked perfectly before)
This is lines 55 - 74
for(let i = fire.length - 1; i > 0; i--) {
fire[i].draw();
fire[i].move();
fire[i].check();
if(fire[i].offscreen()) {
fire.splice(i, 1);
}
}
for(let i = enemy.length - 1; i > 0; i--) {
enemy[i].draw();
enemy[i].move();
if(enemy[i].offscreen()) {
enemy.splice(i, 1);
}
if(enemy[i].contact()) {
enemy[i].kill();
}
}
The entire code is here: https://code.sololearn.com/Wtza5vElEZ9d/?ref=app
(It's less than 200 lines so not really big)
As well as that bug, I am wanting to find out how it would be possible to make the game gradually get faster. I tried having the frameCount be divided/modulos by a variable (that I had called spawnRate) but when I altered the variable in any way, it just stopped spawning the squares all together.
It's also made with p5.js.
Your enemy.contact() function is used in if statement so you should return a boolean with that function.
this.contact = function() {
return dist(playerx, playery, this.x, this.y) <= 20;
}
It would be better if you make function death() in player object.
It will not be so confusing.

Sprite vs Group Collider not working in phaser with enableBody set as true

I'm a bit new to JavaScript and have been playing around with Phaser lately. So I'm building an infinite side scroller and everything works fine except that my player won't collide with the walls. Both sprites have physics enabled and I have tried multiple solutions, none of which work. Can you please help me out?
function bloxo()
{
var game = new Phaser.Game(1200, 600, Phaser.CANVAS, 'gameStage', { preload: preload, create: create, update: update });
var prevHole = 3;
function preload() {
game.load.image('bloxoDown','../bloxo/assets/images/bloxoDown.png');
game.load.image('bloxoUp','../bloxo/assets/images/bloxoUp.png');
game.load.image('wall','../bloxo/assets/images/platform.png',400,200);
var space;
var esc;
var player;
var walls;
var score;
}
function create() {
//Canvas With a White Bacground and Physics is Created
game.stage.backgroundColor = "#ffffff";
game.physics.startSystem(Phaser.Physics.ARCADE);
//Sets the initial Score.
score = 0;
//Sets how fast the tiles move
tileSpeed = -300;
tileWidth = game.cache.getImage('wall').width;
tileHeight = game.cache.getImage('wall').height;;
//Keys for User Input are created
space = game.input.keyboard.addKey(Phaser.Keyboard.SPACEBAR);
esc = game.input.keyboard.addKey(Phaser.Keyboard.ESC);
//Adds Bloxo to the game as a sprite.
player = game.add.sprite(200,200,'bloxoDown');
player.scale.setTo(0.6, 0.6);
game.physics.enable(player, Phaser.Physics.ARCADE);
player.body.collideWorldBounds = true;
player.body.immovable = true;
//Walls Group is created
walls = game.add.physicsGroup();
walls.createMultiple(50, 'wall');
walls.enableBody = true;
game.physics.arcade.overlap(player, walls,null,this)
game.physics.arcade.collide(player,walls,gameOver);
// Stop the following keys from propagating up to the browser
game.input.keyboard.addKeyCapture([ Phaser.Keyboard.SPACEBAR, Phaser.Keyboard.ESC,]);
//Unpausing Function
window.onkeydown = function(event)
{
if (esc.onDown && (esc.timeDown > 2000))
{
if(game.paused)
{
game.paused = !game.paused;
pauseLbl.destroy();
}
}
}
//Add an initial platform
addWall();
//Add a platform every 3 seconds
var timerWorld = game.time.events.loop(500, addWall);
}
function update() {
if (space.isDown)
{
player.body.y -=5;
bloxoUp();
}
else
{
player.body.y +=5;
bloxoDown();
}
if(esc.isDown)
{
pauseGame();
}
}
function bloxoUp()
{
player.loadTexture('bloxoUp');
}
function bloxoDown()
{
player.loadTexture('bloxoDown');
}
function pauseGame()
{
game.paused = true;
pauseLbl = game.add.text(500, 300, 'Game Paused', { font: '30px Roboto', fill: '#aaaaaa' });
}
function addTile(x,y)
{
//Get a tile that is not currently on screen
var tile = walls.getFirstDead();
//Reset it to the specified coordinates
tile.reset(x,y);
tile.body.velocity.x = tileSpeed;
tile.body.immovable = true;
//When the tile leaves the screen, kill it
tile.checkWorldBounds = true;
tile.outOfBoundsKill = true;
}
function addWall()
{
//Speed up the game to make it harder
tileSpeed -= 1;
score += 1;
//Work out how many tiles we need to fit across the whole screen
var tilesNeeded = Math.ceil(game.world.height / tileHeight);
//Add a hole randomly somewhere
do
{
var hole = Math.floor(Math.random() * (tilesNeeded - 2)) + 1;
}while((hole > (prevHole + 2)) && (hole < (prevHole - 2)) );
prevHole = hole;
//Keep creating tiles next to each other until we have an entire row
//Don't add tiles where the random hole is
for (var i = 0; i < tilesNeeded; i++){
if (i != hole && (i != hole+1 && i != hole-1) && (i != hole+2 && i != hole-2)){
addTile(game.world.width, i * tileHeight);
}
}
}
function gameOver()
{
console.log("player hit");
player.kill();
game.state.start(game.state.current);
}
}
You have just to move collide call into your update method:
game.physics.arcade.collide(player, walls, gameOver);
Take a look to the runnable snippet below(I have resized the canvas for the preview, sorry) or Fiddle:
var game = new Phaser.Game(450, 150, Phaser.CANVAS, 'gameStage', {
preload: preload,
create: create,
update: update
});
var prevHole = 3;
function preload() {
game.load.image('bloxoDown', '../bloxo/assets/images/bloxoDown.png');
game.load.image('bloxoUp', '../bloxo/assets/images/bloxoUp.png');
game.load.image('wall', '../bloxo/assets/images/platform.png', 400, 100);
var space;
var esc;
var player;
var walls;
var score;
}
function create() {
//Canvas With a White Bacground and Physics is Created
game.stage.backgroundColor = "#ffffff";
game.physics.startSystem(Phaser.Physics.ARCADE);
//Sets the initial Score.
score = 0;
//Sets how fast the tiles move
tileSpeed = -300;
tileWidth = game.cache.getImage('wall').width;
tileHeight = game.cache.getImage('wall').height;;
//Keys for User Input are created
space = game.input.keyboard.addKey(Phaser.Keyboard.SPACEBAR);
esc = game.input.keyboard.addKey(Phaser.Keyboard.ESC);
//Adds Bloxo to the game as a sprite.
player = game.add.sprite(200, 200, 'bloxoDown');
player.scale.setTo(0.6, 0.6);
game.physics.enable(player, Phaser.Physics.ARCADE);
player.body.collideWorldBounds = true;
player.body.immovable = true;
//Walls Group is created
walls = game.add.physicsGroup();
walls.createMultiple(50, 'wall');
walls.enableBody = true;
game.physics.arcade.overlap(player, walls, null, this)
// remove your call to collide
// Stop the following keys from propagating up to the browser
game.input.keyboard.addKeyCapture([Phaser.Keyboard.SPACEBAR, Phaser.Keyboard.ESC, ]);
//Unpausing Function
window.onkeydown = function(event) {
if (esc.onDown && (esc.timeDown > 2000)) {
if (game.paused) {
game.paused = !game.paused;
pauseLbl.destroy();
}
}
}
//Add an initial platform
addWall();
//Add a platform every 3 seconds
var timerWorld = game.time.events.loop(500, addWall);
}
function update() {
if (space.isDown) {
player.body.y -= 5;
bloxoUp();
} else {
player.body.y += 5;
bloxoDown();
}
// move your collide call here
game.physics.arcade.collide(player, walls, gameOver);
if (esc.isDown) {
pauseGame();
}
}
function bloxoUp() {
player.loadTexture('bloxoUp');
}
function bloxoDown() {
player.loadTexture('bloxoDown');
}
function pauseGame() {
game.paused = true;
pauseLbl = game.add.text(500, 300, 'Game Paused', {
font: '30px Roboto',
fill: '#aaaaaa'
});
}
function addTile(x, y) {
//Get a tile that is not currently on screen
var tile = walls.getFirstDead();
//Reset it to the specified coordinates
if (tile) {
tile.reset(x, y);
tile.body.velocity.x = tileSpeed;
tile.body.immovable = true;
//When the tile leaves the screen, kill it
tile.checkWorldBounds = true;
tile.outOfBoundsKill = true;
}
}
function addWall() {
//Speed up the game to make it harder
tileSpeed -= 1;
score += 1;
//Work out how many tiles we need to fit across the whole screen
var tilesNeeded = Math.ceil(game.world.height / tileHeight);
var prevHole;
//Add a hole randomly somewhere
do {
var hole = Math.floor(Math.random() * (tilesNeeded - 2)) + 1;
} while ((hole > (prevHole + 2)) && (hole < (prevHole - 2)));
prevHole = hole;
//Keep creating tiles next to each other until we have an entire row
//Don't add tiles where the random hole is
for (var i = 0; i < tilesNeeded; i++) {
if (i != hole && (i != hole + 1 && i != hole - 1) && (i != hole + 2 && i != hole - 2)) {
addTile(game.world.width, i * tileHeight);
}
}
}
function gameOver() {
console.log("player hit");
player.kill();
game.state.start(game.state.current);
}
canvas{
border: 5px solid #333;
margin-left:25px;
margin-top:25px;
}
<script src="https://cdnjs.cloudflare.com/ajax/libs/phaser/2.6.2/phaser.min.js"></script>

Not moving through array of Objects?

I have been making a game, my problem is when you click the space key it shoots 1 bullet, but when you do it again nothing happens. I have made it so the game starts with 30 bullets, and they are stored at the top left of screen out of view. When space is clicked they get fired from the tip of your ship using its X, Y values.
Click here to see what I mean:
http://www.taffatech.com/DarkOrbit.html
- as you can see only 1 fires, ever.
Here is the bullet object
function Bullet() //space weapon uses this
{
this.srcX = 0;
this.srcY = 1240;
this.drawX = -20;
this.drawY = 0;
this.width = 11;
this.height = 4;
this.bulletSpeed = 3;
this.bulletReset = -20;
}
Bullet.prototype.draw = function()
{
this.drawX += this.bulletSpeed;
ctxPlayer.drawImage(spriteImage,this.srcX,this.srcY,this.width,this.height,this.drawX,this.drawY,this.width,this.height);
if (this.drawX > canvasWidth)
{
this.drawX = this.bulletReset;
}
}
Bullet.prototype.fire = function(startX, startY)
{
this.drawX = startX;
this.drawY = startY;
}
This is the player Object: (the ship)
function Player() //Object
{
//////Your ships values
this.PlayerHullMax = 1000;
this.PlayerHull = 1000;
this.PlayerShieldMax = 1000;
this.PlayerShield = 347;
this.SpaceCrystal = 2684;
this.Speed = 5; //should be around 2 pixels every-time draw is called by interval, directly linked to the fps global variable
////////////
///////////flags
this.isUpKey = false;
this.isDownKey = false;
this.isLeftKey = false;
this.isRightKey = false;
////////space Weapon
this.noseX = this.drawX + 100;
this.noseY = this.drawY + 30;
this.isSpaceBar = false;
this.isShooting = false;
this.bullets = [];
this.currentBullet = 0;
this.bulletAmount = 30;
for(var i = 0; i < this.bulletAmount; i++) //
{
this.bullets[this.bullets.length] = new Bullet();
}
/////////////
////Pick Ship
this.type = "Cruiser";
this.srcX = PlayerSrcXPicker(this.type);
this.srcY = PlayerSrcYPicker(this.type);
this.drawX = PlayerdrawXPicker(this.type);
this.drawY = PlayerdrawYPicker(this.type);
this.playerWidth = PlayerWidthPicker(this.type);
this.playerHeight = PlayerHeightPicker(this.type);
////
}
Player.prototype.draw = function()
{
ClearPlayerCanvas();
ctxPlayer.globalAlpha=1;
this.checkDirection(); //must before draw pic to canvas because you have new coords now from the click
this.noseX = this.drawX + (this.playerWidth-10);
this.noseY = this.drawY + (this.playerHeight/2);
this.checkShooting();
this.drawAllBullets();
ctxPlayer.drawImage(spriteImage,this.srcX,this.srcY,this.playerWidth,this.playerHeight,this.drawX,this.drawY,this.playerWidth,this.playerHeight);
};
Player.prototype.drawAllBullets = function()
{
for(var i = 0; i < this.bullets.length; i++)
{
if(this.bullets[i].drawX >= 0)
{
this.bullets[i].draw();
}
}
}
Player.prototype.checkShooting = function()
{
if(this.isSpaceBar == true && this.isShooting == false)
{
this.isShooting = true;
this.bullets[this.currentBullet].fire(this.noseX, this.noseY);
this.currentBullet++;
if(this.currentBullet >= this.bullets.length)
{
this.currentBullet = 0;
}
else if(this.isSpaceBar == false)
{
this.isShooting = false;
}
}
}
This is in a method that checks what keys are down:
if (KeyID === 32 ) //spacebar
{
Player1.isSpaceBar = true;
e.preventDefault(); //webpage dont scroll when playing
}
This is in a method that checks what keys are up:
if (KeyID === 32 ) //left and a keyboard buttons
{
Player1.isSpaceBar = false;
e.preventDefault(); //webpage dont scroll when playing
}
Any other info you need just ask!
Okay, I think I figured it out
try adding isShooting false to the key up event
if (KeyID === 32 ) //left and a keyboard buttons
{
Player1.isSpaceBar = false;
Player1.isShooting = false;
e.preventDefault(); //webpage dont scroll when playing
}

How to handle multiple keypresses with canvas

Using something like:
window.addEventListener("keydown", handleFn, true);
How would I be able to handle multiple keypresses at the same time, for multiplayer use? Multiple people would be using one keyboard, so like the Q and P keys would be pressed at the same time to move different objects on screen.
I don't have any keyup handles yet and wonder if that would solve this.
The logic I have so far is something like:
if keydown == Q
paddle.left = true;
...
//game loop
if paddle.left == true
paddle.x -= 1;
paddle.left = false;
Players can be expected to hold the button(s) as well.
This is how I generally do it. First you need an array to hold the keystates.
var keys=[];
Then setup your event listeners.
// key events
document.body.addEventListener("keydown", function (e) {
keys[e.keyCode] = true;
});
document.body.addEventListener("keyup", function (e) {
keys[e.keyCode] = false;
});
What the following does is set an item in the array to either true or false, corresponding to that keys code.
Then you just need to use some conditions to see what is pressed and what you should do.
// check the keys and do the movement.
if (keys[38]) {
if (velY > -speed) {
velY--;
}
}
if (keys[40]) {
if (velY < speed) {
velY++;
}
}
if (keys[39]) {
if (velX < speed) {
velX++;
}
}
if (keys[37]) {
if (velX > -speed) {
velX--;
}
}
Below is a demo where you can move around and mess with multiple key presses. Use wasd, and the arrow keys.
Live Demo
var canvas = document.getElementById("canvas"),
ctx = canvas.getContext("2d");
canvas.width = canvas.height = 300;
var player1 = {
x: 50,
y: 150,
velY: 0,
velX: 0,
color: "blue"
},
player2 = {
x: 250,
y: 150,
velY: 0,
velX: 0,
color: "red"
};
var x = 150,
y = 150,
velY = 0,
velX = 0,
speed = 2,
friction = 0.98,
keys = [];
function update() {
if (keys[38]) {
if (player1.velY > -speed) {
player1.velY--;
}
}
if (keys[40]) {
if (player1.velY < speed) {
player1.velY++;
}
}
if (keys[39]) {
if (player1.velX < speed) {
player1.velX++;
}
}
if (keys[37]) {
if (player1.velX > -speed) {
player1.velX--;
}
}
if (keys[87]) {
if (player2.velY > -speed) {
player2.velY--;
}
}
if (keys[83]) {
if (player2.velY < speed) {
player2.velY++;
}
}
if (keys[68]) {
if (player2.velX < speed) {
player2.velX++;
}
}
if (keys[65]) {
if (player2.velX > -speed) {
player2.velX--;
}
}
ctx.clearRect(0, 0, 300, 300);
updatePlayer(player1);
updatePlayer(player2);
setTimeout(update, 10);
}
function updatePlayer(player) {
player.velY *= friction;
player.y += player.velY;
player.velX *= friction;
player.x += player.velX;
if (player.x >= 295) {
player.x = 295;
} else if (player.x <= 5) {
player.x = 5;
}
if (player.y > 295) {
player.y = 295;
} else if (player.y <= 5) {
player.y = 5;
}
ctx.fillStyle = player.color;
ctx.beginPath();
ctx.arc(player.x, player.y, 5, 0, Math.PI * 2);
ctx.fill();
}
update();
document.body.addEventListener("keydown", function (e) {
keys[e.keyCode] = true;
});
document.body.addEventListener("keyup", function (e) {
keys[e.keyCode] = false;
});
You could try a pattern like this:
(function game(){
// canvas setup ...
// set up a "hash" of keycodes associated with whether or not they
// are pressed, and what should happen when they are pressed.
var keys = {
37:{down:false, action:function(){player1.velX--;}},
38:{down:false, action:function(){player1.velY--;}},
39:{down:false, action:function(){player1.velX++;}},
40:{down:false, action:function(){player1.velY++;}},
65:{down:false, action:function(){player2.velX--;}},
68:{down:false, action:function(){player2.velX++;}},
83:{down:false, action:function(){player2.velY++;}},
87:{down:false, action:function(){player2.velY--;}},
};
document.body.addEventListener("keydown", function (e) {
if(keys[e.keyCode]) keys[e.keyCode].down = true;
});
document.body.addEventListener("keyup", function (e) {
if(keys[e.keyCode]) keys[e.keyCode].down = false;
});
(function update() {
ctx.clearRect(...);
for(var key in keys)
if(keys[key].down)
keys[key].action();
// redraw players.
requestAnimationFrame(update);
})();
})();
The nice thing about this setup is that it associates the actions directly with the keys, allows you to add more key-actions easily, and allows for a great amount of flexibility with the possibility of easily adding/removing key presses at runtime, and even changing what a particular key does at any given time.

Canvas fade in/out functions not working as expected

So I have these functions to fade a canvas in and out that aren't working the way I expect them to. Here's what I'm working with at the moment:
function fade_out ()
{
var canvas = document.getElementById("builder");
var context = canvas.getContext('2d');
console.log(context.globalAlpha);
context.globalAlpha -= 0.01;
if(context.globalAlpha > 0)
{
setTimeout(fade_out, 5);
}
}
function fade_in ()
{
var canvas = document.getElementById("builder");
var context = canvas.getContext('2d');
context.globalAlpha += 0.01;
if(context.globalAlpha < 1)
{
setTimeout(fade_in, 5);
}
}
My intent was to make it a half second fade. What I ended up with was it just blinking in and out in a flash. The console.log in the first function tells me it's not even close to working the way I expect it to. What went wrong here?
EDIT: There seems to be an endless loop going, and the context.globalAlpha is getting into 20 significant digits, even though I didn't use numbers like that.
function fade_in() {
setTimeout( function() {
var cn = document.getElementById("builder");
var ct = cn.getContext('2d').globalAlpha;
ct += 0.02;
if(ct >= 1) {
ct=1;
}
if (ct < 1) {
fade_in();
}
else {
return false;
}
}, 30);
}
function fade_out() {
setTimeout( function() {
var cn = document.getElementById("builder");
var ct = cn.getContext('2d').globalAlpha;
ct -= 0.02;
if(ct <= 0) {
ct=0;
}
if (ct > 0) {
fade_out();
}
else {
return false;
}
}, 30);
}

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