How do you code jumping in a javascript game? - javascript

I am writing a game in javascript for the first time most of my code is not efficient. I am stuck on how to code a jumping method for my cube(the character for my game). The jump works but the player can double jump. The double jump occurs on the way down if the user presses the jump key again. I have tried setting a variable which will be modified when the player is on the ground and if it is true then your only allowed to jump but it hasn't worked. Here is the code:
//setting screen up
const canvas = document.getElementById('canvas');
const c = canvas.getContext('2d');
canvas.width = innerWidth;
canvas.height = innerHeight;
//ground
gHeight = canvas.height/1.3
function ground(){
c.fillStyle = 'white';
c.fillRect(0,gHeight,canvas.width,canvas.height-gHeight);
}
//player
class Player{
constructor(x,y,w,h){
this.x = x;
this.y = y;
this.w = w;
this.h = h;
this.color = 'rgb(92,168,255)';
this.l = false;
this.r = false;
this.speed = 10
this.hp = 100;
this.jump = false;
this.jumpC = 0;
}
draw(){
c.fillStyle = this.color;
c.fillRect(this.x,this.y,this.w,this.h);
}
update(){
this.draw();
//gravity
if(this.y < gHeight - this.h){
this.y += 5;
}
//movement
if(this.l == true){
this.x -= this.speed;
}
if(this.r == true){
this.x += this.speed;
}
//jump
if(this.jump == true){
this.y -= 10;
this.jumpC += 5;
}
if (this.jumpC >= 100){
this.jump = false;
this.jumpC = 0;
}
}
}
var player = new Player(100, 100,50,50);
//main loop
var animationId;
function animate(){
c.fillStyle = 'rgba(0,0,0,0.7)';
c.fillRect(0,0, canvas.width, canvas.height);
animationId = requestAnimationFrame(animate);
//drawing the ground
ground();
//drawing the player
player.update();
//ending game
if(player.hp == 0){
cancelAnimationFrame(animationId);
}
}
//keypress
addEventListener('keydown', (event)=>{
if(event.keyCode == 37) {
player.l = true;
}
if(event.keyCode == 39) {
player.r = true;
}
if(event.keyCode == 38 && player.jump == false){
player.jump = true;
}
});
//keyup
addEventListener('keyup', (event)=>{
if(event.keyCode == 37 ) {
player.l = false;
}
if(event.keyCode == 39) {
player.r = false;
}
});
animate();
tell me if more info is needed

After the jump make it impossible to jump until the player reaches the ground.
if(event.keyCode == 38 && player.jump == false){ player.jump = true; }
I would add another comparison in this if like this:
if(event.keyCode == 38 && player.jump == false && player.isOnGround()){ player.jump = true; }
To check if the user landed

Related

Difficulty Adding a "Play Again!" Button to this snake game

I've been trying to figure out how I can add a play again button to refresh the page after a player has lost. This is a classic snake game. I followed a tutorial on it and but they never said anything about a Play Again button. Any help would be appreciated. Nothing too complicated though please, I'm still learning.
const ctx = canvas.getContext("2d");
class SnakePart {
constructor(x, y) {
this.x = x;
this.y = y;
}
}
let speed = 7;
let tileCount = 20;
let tileSize = canvas.width / tileCount - 2;
let headX = 10;
let headY = 10;
const snakeParts = [];
let tailLength = 2;
let appleX = 5;
let appleY = 5;
let inputsXVelocity = 0;
let inputsYVelocity = 0;
let xVelocity = 0;
let yVelocity = 0;
let score = 0;
const gulpSound = new Audio("gulp.mp3");
//game loop
function drawGame() {
xVelocity = inputsXVelocity;
yVelocity = inputsYVelocity;
changeSnakePosition();
let result = isGameOver();
if (result) {
return;
}
clearScreen();
checkAppleCollision();
drawApple();
drawSnake();
drawScore();
if (score > 5) {
speed = 9;
}
if (score > 10) {
speed = 11;
}
setTimeout(drawGame, 1000 / speed);
}
function isGameOver() {
let gameOver = false;
if (yVelocity === 0 && xVelocity === 0) {
return false;
}
//walls
if (headX < 0) {
gameOver = true;
} else if (headX === tileCount) {
gameOver = true;
} else if (headY < 0) {
gameOver = true;
} else if (headY === tileCount) {
gameOver = true;
}
for (let i = 0; i < snakeParts.length; i++) {
let part = snakeParts[i];
if (part.x === headX && part.y === headY) {
gameOver = true;
break;
}
}
if (gameOver) {
ctx.fillStyle = "white";
ctx.font = "50px Verdana";
if (gameOver) {
ctx.fillStyle = "white";
ctx.font = "50px Verdana";
var gradient = ctx.createLinearGradient(0, 0, canvas.width, 0);
gradient.addColorStop("0", " magenta");
gradient.addColorStop("0.5", "blue");
gradient.addColorStop("1.0", "red");
// Fill with gradient
ctx.fillStyle = gradient;
ctx.fillText("Game Over!", canvas.width / 6.5, canvas.height / 2);
}
ctx.fillText("Game Over!", canvas.width / 6.5, canvas.height / 2);
}
return gameOver;
}
function drawScore() {
ctx.fillStyle = "white";
ctx.font = "10px Verdana";
ctx.fillText("Score " + score, canvas.width - 50, 10);
}
function clearScreen() {
ctx.fillStyle = "black";
ctx.fillRect(0, 0, canvas.width, canvas.height);
}
function drawSnake() {
ctx.fillStyle = "green";
for (let i = 0; i < snakeParts.length; i++) {
let part = snakeParts[i];
ctx.fillRect(part.x * tileCount, part.y * tileCount, tileSize, tileSize);
}
snakeParts.push(new SnakePart(headX, headY)); //put an item at the end of the list next to the head
while (snakeParts.length > tailLength) {
snakeParts.shift(); // remove the furthet item from the snake parts if have more than our tail size.
}
ctx.fillStyle = "orange";
ctx.fillRect(headX * tileCount, headY * tileCount, tileSize, tileSize);
}
function changeSnakePosition() {
headX = headX + xVelocity;
headY = headY + yVelocity;
}
function drawApple() {
ctx.fillStyle = "red";
ctx.fillRect(appleX * tileCount, appleY * tileCount, tileSize, tileSize);
}
function checkAppleCollision() {
if (appleX === headX && appleY == headY) {
appleX = Math.floor(Math.random() * tileCount);
appleY = Math.floor(Math.random() * tileCount);
tailLength++;
score++;
gulpSound.play();
}
}
document.body.addEventListener("keydown", keyDown);
function keyDown(event) {
//up
if (event.keyCode == 38 || event.keyCode == 87) {
//87 is w
if (inputsYVelocity == 1) return;
inputsYVelocity = -1;
inputsXVelocity = 0;
}
//down
if (event.keyCode == 40 || event.keyCode == 83) {
// 83 is s
if (inputsYVelocity == -1) return;
inputsYVelocity = 1;
inputsXVelocity = 0;
}
//left
if (event.keyCode == 37 || event.keyCode == 65) {
// 65 is a
if (inputsXVelocity == 1) return;
inputsYVelocity = 0;
inputsXVelocity = -1;
}
//right
if (event.keyCode == 39 || event.keyCode == 68) {
//68 is d
if (inputsXVelocity == -1) return;
inputsYVelocity = 0;
inputsXVelocity = 1;
}
}
drawGame();```
The easiest way to refresh the page would be just:
window.location.reload(false)
Source:
https://www.freecodecamp.org/news/location-reload-method-how-to-reload-a-page-in-javascript/
I would suggest that simply reloading the page is not a great way to implement a play again feature but I appreciate the creativity of it.

can not rotate a rectangular shape in canvas

I am new in HTML5 canvas. I am trying to build game area using HTML canvas where someone can drive around a car inside
Canvas area like if I press the left arrow key the car will turn to the left and if press the right arrow key the car will turn to the right side. And up and down arrow keys are responsible for moving the car upward or downward. And the car must stay within the canvas area. Here, I use rotate method to turn the car right or left. But it is not working, actually the car is getting away from the canvas and behaving like a crap.
Anyone has any idea to solve the problem? I am totally stuck here. Thanks in advance.
Initially I am displaying a rectangle instead of car.
My js file is given below.
const canvas = document.querySelector("canvas");
const ctx = canvas.getContext("2d");
canvas.width = innerWidth - 100;
canvas.height = innerHeight - 100;
const canvasW = canvas.width;
const canvasH = canvas.height;
let upPressed = false,
downPressed = false,
rightPressed = false,
leftPressed = false;
class PlayerCar {
constructor(carX, carY, carWidth, carHeight) {
this.carX = carX;
this.carY = carY;
this.carWidth = carWidth;
this.carHeight = carHeight;
}
draw() {
ctx.fillStyle = "blue";
ctx.beginPath();
ctx.rect(this.carX, this.carY, this.carWidth, this.carHeight);
ctx.fill();
ctx.closePath();
}
}
const playerCar = new PlayerCar(100, 100, 40, 60);
playerCar.draw();
function navigation() {
const handleKeyDown = (e) => {
if (e.key === "ArrowUp") {
upPressed = true;
}
if (e.key === "ArrowDown") {
downPressed = true;
}
if (e.key === "ArrowRight") {
rightPressed = true;
}
if (e.key === "ArrowLeft") {
leftPressed = true;
}
};
const handleKeyUp = (e) => {
if (e.key === "ArrowUp") {
upPressed = false;
}
if (e.key === "ArrowDown") {
downPressed = false;
}
if (e.key === "ArrowRight") {
rightPressed = false;
}
if (e.key === "ArrowLeft") {
leftPressed = false;
}
};
document.addEventListener("keydown", handleKeyDown);
document.addEventListener("keyup", handleKeyUp);
}
function animate() {
requestAnimationFrame(animate);
ctx.clearRect(0, 0, canvasW, canvasH);
if (upPressed) {
playerCar.carY -= 5;
}
if (downPressed) {
playerCar.carY += 5;
}
if (leftPressed) {
ctx.save();
ctx.translate(
playerCar.carX + playerCar.width / 2,
playerCar.carY + playerCar.height / 2
);
ctx.rotate((Math.PI / 180) * 0.2);
playerCar.carX -= 5;
ctx.restore();
}
if (rightPressed) {
ctx.save();
ctx.translate(
playerCar.carX + playerCar.width / 2,
playerCar.carY + playerCar.height / 2
);
ctx.rotate((Math.PI / 180) * -0.2);
playerCar.carX += 5;
ctx.restore();
}
if (playerCar.carX < 0) playerCar.carX = 0;
if (playerCar.carX > canvasW - playerCar.carWidth)
playerCar.carX = canvasW - playerCar.carWidth;
if (playerCar.carY < 0) playerCar.carY = 0;
if (playerCar.carY > canvasH - playerCar.carHeight)
playerCar.carY = canvasH - playerCar.carHeight;
playerCar.draw();
}
function startGame() {
animate();
}
startGame();
navigation();
I would first move all of the update info to a method in the car class vice doing it in the animate loop.
This is where cos and sin come in and getting familiar with angles. You also must understand the canvas relation the the object it draws is always at (x, y) of (0, 0) unless you translate it to the center. To do that draw your object in this manner:
ctx.fillStyle = "blue";
ctx.save();
ctx.beginPath();
ctx.translate(this.carX, this.carY)
ctx.rotate(this.angle)
ctx.rect(-this.carWidth/2, -this.carHeight/2, this.carWidth, this.carHeight);
ctx.fill();
ctx.closePath();
ctx.restore();
Use of save() and restore() are a must unless you want to translate and rotate you object back to its original. It's the same ting but simpler. So now I am translating the car around the canvas and the car itself is drawn at negative half the width and height to ensure the canvas (0, 0) corner is in the center of the car. This is because canvas always rotates from the top-left corner.
Now create a method called update() and put you control logic in there:
update() {
if (rightPressed) {
this.angle += this.rot
} else if (leftPressed) {
this.angle -= this.rot
}
if (upPressed) {
this.carX += Math.cos(this.angle+toRadians(-90)) * 5;
this.carY += Math.sin(this.angle+toRadians(-90)) * 5;
}
}
Be aware I added angle and rot to the constructor also. What this is doing is when you press left or right the car rotate accordingly. As for pressing up we are going to translate it by the rotation. Since this would normally make the car drive to the right we have to also add -90 degrees to the current angle to ensure the car drives forwards. Just remove +toRadians(-90) and see what happens.
Multiplying it by 5 is an arbitrary number for speed. You can even make it part of the constructor and set it there. i.e. this.speed = 5
Doing the same thing for downPressed but instead use +toRadians(90)
toRadians() is just a simple function added to your code to convert degrees to radians.
const canvas = document.querySelector("canvas");
const ctx = canvas.getContext("2d");
canvas.width = 600;
canvas.height = 600;
const canvasW = canvas.width;
const canvasH = canvas.height;
let upPressed = false,
downPressed = false,
rightPressed = false,
leftPressed = false;
class PlayerCar {
constructor(carX, carY, carWidth, carHeight) {
this.carX = carX;
this.carY = carY;
this.carWidth = carWidth;
this.carHeight = carHeight;
this.angle = 0;
this.rot = 0.1; //control how fast it turns
}
draw() {
ctx.fillStyle = "blue";
ctx.save();
ctx.beginPath();
ctx.translate(this.carX, this.carY)
ctx.rotate(this.angle)
ctx.rect(-this.carWidth/2, -this.carHeight/2, this.carWidth, this.carHeight);
ctx.fill();
ctx.closePath();
ctx.restore();
}
update() {
if (rightPressed) {
this.angle += this.rot
} else if (leftPressed) {
this.angle -= this.rot
}
if (upPressed) {
this.carX += Math.cos(this.angle+toRadians(-90)) * 5;
this.carY += Math.sin(this.angle+toRadians(-90)) * 5;
}
if (downPressed) {
this.carX += Math.cos(this.angle+toRadians(90)) * 5;
this.carY += Math.sin(this.angle+toRadians(90)) * 5;
}
}
}
function toRadians(deg) {
return (deg * Math.PI) / 180;
}
const playerCar = new PlayerCar(100, 100, 40, 60);
playerCar.draw();
function navigation() {
const handleKeyDown = (e) => {
if (e.key === "ArrowUp") {
upPressed = true;
}
if (e.key === "ArrowDown") {
downPressed = true;
}
if (e.key === "ArrowRight") {
rightPressed = true;
}
if (e.key === "ArrowLeft") {
leftPressed = true;
}
};
const handleKeyUp = (e) => {
if (e.key === "ArrowUp") {
upPressed = false;
}
if (e.key === "ArrowDown") {
downPressed = false;
}
if (e.key === "ArrowRight") {
rightPressed = false;
}
if (e.key === "ArrowLeft") {
leftPressed = false;
}
};
document.addEventListener("keydown", handleKeyDown);
document.addEventListener("keyup", handleKeyUp);
}
function animate() {
requestAnimationFrame(animate);
ctx.clearRect(0, 0, canvasW, canvasH);
if (playerCar.carX < 0) playerCar.carX = 0;
if (playerCar.carX > canvasW - playerCar.carWidth)
playerCar.carX = canvasW - playerCar.carWidth;
if (playerCar.carY < 0) playerCar.carY = 0;
if (playerCar.carY > canvasH - playerCar.carHeight)
playerCar.carY = canvasH - playerCar.carHeight;
playerCar.draw();
playerCar.update();
}
function startGame() {
animate();
}
startGame();
navigation();
<canvas></canvas>
To be clear on why your code is not doing what you expect think about this. You are trying to translate and rotate the context without ever accessing the object. If you were to add ctx.fillRect() to your animate loop would you think it's going to just know that you want to change the car? Same goes for translate and rotate. Try adding a fillStyle and fillRect to your rightPressed
if (rightPressed) {
ctx.save();
playerCar.carX += 5;
ctx.translate(
playerCar.carX + playerCar.width / 2,
playerCar.carY + playerCar.height / 2
);
ctx.rotate(45);
ctx.fillStyle = 'grey'
ctx.fillRect(0, 0, canvas.width, canvas.height)
ctx.restore();
}
You will see when you press right the context does what you want just not the context of the object. This is why adding it directly top the class should be done. Now you are specifically targeting the object you want.

pong paddle won't move correctly

I'm making pong to get better at javascript but the player paddle doesn't move when the left key is pressed, and if I press the right key it doesn't stop going right.
I've checked the capitalization, semicolons, and rearranged the code but nothing changed.
var rightPressed = false;
var leftPressed = false;
var paused = false;
document.addEventListener("keydown", keyDownHandler, false);
document.addEventListener("keyup", keyUpHandler, false);
function keyDownHandler(e) {
if(e.keyCode == 39) {
rightPressed = true;
}
else if(e.keycode == 37) {
leftPressed = true;
}
else if(e.keycode == 32) {
paused = !paused;
}//pauses or unpause game
}
//handles when a key isn't being pushed
function keyUpHandler(e) {
if(e.keycode == 39) {
rightPressed = false;
}//tells our code that right isnt being pressed
else if(e.keyCode == 37) {
leftPressed = false;
}//tells code left isnt being pressed
}
var paddleHeight = 10;
var paddleWidth = 75;
var paddleX = (canvas.width-paddleWidth)/2;
var paddleY = canvas.height-paddleHeight-10;
function drawPaddle() {
ctx.fillRect(paddleX,paddleY,paddleWidth,paddleHeight);
ctx.fillStyle = "white";
}
function draw() {
ctx.clearRect(0, 0, canvas.width, canvas.height);
drawBall();
drawPaddle();
if (!paused){//what to do when paused
if (x + dx > canvas.width - ballRadius || x + dx < ballRadius) {
dx = -dx;
}
if (y + dy < ballRadius) {
dy = -dy;
}
if (rightPressed && paddleX < canvas.width-paddleWidth) {
paddleX += 7;
}
else if(leftPressed && paddleX > 0) {
paddleX -= 7;}
x += dx;
y += dy;
//velocity
}
}
The paddle should move right when I press the right arrow key, left when I press the left arrow key, and pause when I hit the spacebar. Instead it doesn't go left or pause and won't stop going right.

javascript jumping character not working

I'm having a few issues with my code. Can't get my cube to jump. Take a look at my code and let me know if you can help please.
My left, right and duck abilities all currently work at desired level, but I cannot get my cube to jump. I've been trying for three days and can't find anything online. My javascript is embedded within a tag in a html page.
var canvas = document.getElementById("gameCanvas");
var ctx = canvas.getContext("2d");
var coinRad = 8;
var coinX = 40;
var coinY = 80;
var x = 20;
var y = 510;
var w = 30;
var h = 50;
var rightPressed = false;
var leftPressed = false;
var ducked = false;
var jumping = false;
document.addEventListener("keydown", keyDownHandler, false);
document.addEventListener("keyup", keyUpHandler, false);
function keyDownHandler(e) {
if (e.keyCode == 39) {
rightPressed = true;
} else if (e.keyCode == 37) {
leftPressed = true;
} else if (e.keyCode == 40) {
ducked = true;
} else if (e.keycode == 32) {
jumping = true;
}
}
function keyUpHandler(e) {
if (e.keyCode == 39) {
rightPressed = false;
} else if (e.keyCode == 37) {
leftPressed = false;
} else if (e.keyCode == 40) {
ducked = false;
} else if (e.keycode == 32) {
jumping = false;
}
}
function drawCube() {
ctx.beginPath();
ctx.rect(x, y, w, h);
ctx.fillStyle = "Green";
ctx.fill();
ctx.closePath();
}
function run() {
ctx.clearRect(0, 0, canvas.width, canvas.height);
if (leftPressed) {
if (x > 0) {
x -= 2.5;
}
} else if (rightPressed) {
if (x < canvas.width - w) {
x += 2.5;
}
}
if (jumping) {
y -= 10;
h -= 10;
}
if (ducked) {
y = 535;
h = 25;
} else {
y = 510;
h = 50;
}
drawCube();
}
setInterval(run, 10);
<canvas id="gameCanvas"></canvas>
Additionally, your keyCode check is improperly capitalized for the jumping condition.
else if (e.keyCode == 40) {
ducked = false;
} else if (e.keycode == 32) { //should be keyCode
jumping = false;
}
because when the run method end, you do this.
if (jumping) {
y -= 10;
h -= 10;
}
if (ducked) {
y = 535;
h = 25;
} else {
y = 510;
h = 50;
}
even if you change the values from Y and H, their values always change to 510 and 50 respectively, because the else in ducked condition.
Remove this else or find another logic to do the same

Drawing an arc in java script but it doesn't appear

I'm working on a simple html/js project to get a box moving in a canvas that can shoot a ball. I got the box moving but I cant get the ball to appear. The program makes it to the drawBall() and moveBall()(Tested using alerts) functions but they don't do anything. I've been working on this the past hour and so and I just can't get it to work. Here's my javascript code that moves the box and should draw a ball whenever the spacebar is released.
function init() {
//canvas = document.getElementById('canvas');
context = $('#canvas')[0].getContext('2d');
WIDTH = $('#canvas').width();
HEIGHT = $('#canvas').height();
block_x = WIDTH / 2;
block_y = HEIGHT / 2;
setInterval('draw()', 25);
}
function clearCanvas() {
context.clearRect(0,0,WIDTH,HEIGHT);
}
function draw() {
clearCanvas();
if(shotBall)
{
drawBall();
moveBall();
}
if (rightKey) block_x += 5;
else if (leftKey) block_x -= 5;
if (upKey) block_y -= 5;
else if (downKey) block_y += 5;
if (block_x <= 0) block_x = 0;
if ((block_x + block_w) >= WIDTH) block_x = WIDTH - block_w;
if (block_y <= 0) block_y = 0;
if ((block_y + block_h) >= HEIGHT) block_y = HEIGHT - block_h;
context.fillRect(block_x, block_y, block_w, block_h);
}
function drawBall() {
context.beginPath();
context.arc(ball_x, ball_y, ball_radius, 0, Math.PI * 2, false);
}
function moveBall() {
ball_y += 1;
ball_x -= 1;
}
function onKeyDown(evt) {
if (evt.keyCode == 68) rightKey = true;
else if (evt.keyCode == 65) leftKey = true;
if (evt.keyCode == 87) upKey = true;
else if (evt.keyCode == 83) downKey = true;
}
function onKeyUp(evt) {
if (evt.keyCode == 68) rightKey = false;
else if (evt.keyCode == 65) leftKey = false;
if (evt.keyCode == 87) upKey = false;
else if (evt.keyCode == 83) downKey = false;
if(evt.keyCode == 32) createBall();
}
function createBall()
{
ball_x = block_x + (block_w / 2);
ball_y = block_y + (block_y / 2);
radius = 20;
shotBall = true;
}
$(document).keydown(onKeyDown);
$(document).keyup(onKeyUp);
When I tried your code
the problem that I can see is that you haven't initialized the block_w, and block_h and the ball_radius variables, because these values are seems to be undefined as I see in firebug tool.
So you have to make sure that you have defined and initialized every variable that you use.
Also You have to make sure that you are calling every function that you have defined.
When I put values manually in the context.arc(23, 34, 45, 0, Math.PI*2, false); function
then it works fine for me.
So make sure you have defined and initialized every variable.

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