Develop Reference

how to define a color for an instance of a class in Java Scipt

I've making a breakout game and I had to make some blocks and give them random colors defined in a array, but for making more blocks I had to use a for loop. So, when I add them to my update function, colors are flashing at frame rate. I think you'll understand better if you run the snippet
one more thing: that canvasRendering...rundedRectangle is a function that draws rounded edge rectangles someone please find a solution!
CanvasRenderingContext2D.prototype.roundedRectangle = function(x, y, width, height, rounded) {
const radiansInCircle = 2 * Math.PI;
const halfRadians = (2 * Math.PI)/2;
const quarterRadians = (2 * Math.PI)/4 ;
// top left arc
this.arc(rounded + x, rounded + y, rounded, -quarterRadians, halfRadians, true);
// line from top left to bottom left
this.lineTo(x, y + height - rounded);
// bottom left arc
this.arc(rounded + x, height - rounded + y, rounded, halfRadians, quarterRadians, true) ;
// line from bottom left to bottom right
this.lineTo(x + width - rounded, y + height);
// bottom right arc
this.arc(x + width - rounded, y + height - rounded, rounded, quarterRadians, 0, true) ;
// line from bottom right to top right
this.lineTo(x + width, y + rounded) ;
// top right arc
this.arc(x + width - rounded, y + rounded, rounded, 0, -quarterRadians, true) ;
// line from top right to top left
this.lineTo(x + rounded, y) ;
};
var canvas= document.getElementById("gameCanvas");
var ctx = canvas.getContext("2d");
function Player(x,y,w,h){
this.x = x;
this.y = y;
this.w = w;
this.h = h;
this.show = function(){
ctx.beginPath();
ctx.rect(this.x, this.y, this.w, this.h);
ctx.fillStyle = "#ffff";
ctx.fill();
ctx.closePath();
};
this.move = function(speed){
this.x += speed;
};
}
function Ball(x,y,r){
this.x = x;
this.y = y;
this.r = r;
this.show = function(){
ctx.beginPath();
ctx.arc(this.x,this.y,this.r,0,2* Math.PI);
ctx.fillStyle = "tomato";
ctx.fill();
ctx.closePath();
};
this.move= function(speedX,speedY){
this.show();
this.speed = 2;
this.x += speedX;
this.y += speedY;
};
}
var colors = ['#A5E75A','#7254AD','#FFD606','#FF093D'];
function Block(x,y,w,h){
this.x = x;
this.y = y;
this.w = w;
this.h = h;
this.status =1;
this.show= function(color){
ctx.beginPath();
ctx.roundedRectangle(this.x,this.y,this.w,this.h,5);
//ctx.arc(this.x,this.y,10,0,2*Math.PI);
//ctx.fillStyle = colors[Math.floor(Math.random()*colors.length)];
ctx.fillStyle = color;
ctx.fill();
ctx.closePath();
};
}
var player = new Player(canvas.width/2-50,780,100,20);
var ball = new Ball(player.x+player.w/2, player.y,15);
var rigthPressed = false;
var leftPressed = false;
var blocks = [];
var rowCount = 5;
var columnCount = 6;
var noInRow = 6;
var blockCount = (rowCount*columnCount)+1;
var rc = {blockRow : 0,
blockCol : 0};
for(let i = 0; i < blockCount; i++){
blocks.push(new Block(rc.blockCol*60+25,rc.blockRow*60-30,50,50));
rc.blockCol++;
if(i % noInRow === 0){
rc.blockRow++;
rc.blockCol = 0;
}
}
window.addEventListener("keydown", function(e){
if(e.keyCode == 39){
rigthPressed = true;
}
if(e.keyCode == 37){
leftPressed = true;
}
});
window.addEventListener("keyup", function(e){
if(e.keyCode == 39){
rigthPressed = false;
}
if(e.keyCode == 37){
leftPressed = false;
}
});
function objMovement(){
if(rigthPressed){
player.move(5);
if (player.x > canvas.width-player.w){
player.x = canvas.width-player.w;
}
}
if(leftPressed){
player.move(-5);
if(player.x < 0){
player.x = 0;
}
}
if(ball.x > canvas.width-ball.r || ball.x < 0+ball.r){
ballSpeedX = -ballSpeedX;
}
if (/*ball.y > canvas.height-ball.r ||*/ball.y < 0+ball.r){
ballSpeedY = -ballSpeedY;
}
if(ball.x<player.x+player.w &&ball.x>player.x && ball.y>player.y && ball.y<player.y+player.h){
ballSpeedY = -ballSpeedY;
ballSpeedX= ballSpeedX;
}
function Bump(){
if (ball.x>player.x && ball.x<player.x+player.w/2){
if (ball.y >= player.y){
ballSpeedX = -5;
}
}
if(ball.x>player.x+player.w/2 && ball.x<player.x+player.w){
if(ball.y >= player.y){
ballSpeedX = 5;
}
}
}
//Bump();
}
function reload(){
if (ball.y>canvas.height){
//alert('gameOver');
ball.x =player.x+player.w/2;
ball.y = player.y-ball.r;
ballSpeedX = 0;
ballSpeedY = 0;
}
}
var ballSpeedX = 0;
var ballSpeedY = -0;
function collision(){
for(let i=1;i<blockCount;i++){
if(ball.x>blocks[i].x &&
ball.x<blocks[i].x+blocks[i].w &&
ball.y>blocks[i].y &&
ball.y<blocks[i].y+blocks[i].h){
blocks[i].status = 0;
ballSpeedY = -ballSpeedY;
blocks.splice(i,1);
blockCount--;
//ballSpeedX = 0;
//ballSpeedY = 0;
console.log('hit');
}
}
}
function update(){
ctx.clearRect(0,0,canvas.width,canvas.height);
objMovement();
for(let i=1;i<blockCount;i++){
if(blocks[i].status == 1){
blocks[i].show(colors[Math.floor(Math.random()*colors.length)]);
}
}
collision();
ball.show();
ball.move(ballSpeedX,ballSpeedY);
player.show();
reload();
window.requestAnimationFrame(update);
}
update();
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>🌝🌝</title>
<style>
#body{
background-color: rgb(31, 30, 30);
}
#gameCanvas{
border: 15px solid rgb(44, 44, 44);
border-radius: 20px;
background-color:rgb(19, 18, 18);
margin: 250px;
}
</style>
</head>
<body id="body">
<canvas id="gameCanvas" width=400 height=800></canvas>
<script type="text/javascript" src="./index.js"></script>
</body>
</html>

Because you remove and redraw all rectangles from the canvas each update and assign a new color on show, they get assigned a new color each update. You might be able to avert this by adding a property color to the rectangle, which is initialised (once, so in the initial for loop) with a random color, and alter the show function to use this.color rather than accept a color as an argument. This way, you don't assign a new color to a rectangle each update, and it won't change color each update.

detecting collisions on the canvas

im trying to make a game where collisions happen between the protagonist and the antagonist. I cant get the collision to work though, i've tried using the x and y position then the x and y positions plus the width and the height of the protagonist and the antagonist
var canvas = document.getElementById('canvas');
var PX = 10;
var PY = 10;
var PW = 10;
var PH = 10;
var P = PX + PY;
var EX1 = 100;
var EY1 = 100;
var EW1 = 10;
var EH1 = 10;
var E1 = EX1 + EY1;
window.addEventListener("keydown", charMove);
window.addEventListener("keyup", charMove);
window.addEventListener("keypress", charMove);
window.onload = function() {
context = canvas.getContext("2d");
canvas.style.background = "black";
var framesPerSecond = 30;
setInterval(function() {
draw();
move();
}, 1000/framesPerSecond);
}
function draw() {
//EX context.fillRect(PosX, PosY, width, height);
//draws protagonist
context.beginPath();
context.clearRect(0, 0, canvas.width, canvas.height);
context.fillStyle = "blue"
context.fillRect(PX, PY, PW, PH);
context.stroke();
context.closePath();
//draws antagonist(s)
context.beginPath();
context.fillStlyle = "red";
context.fillRect(EX1, EY1, EW1, EH1);
context.stroke();
context.closePath();
}
function move() {
}
function charMove(){
var x = event.which || event.keyCode;
if(x == 37){
PX -= 1;
}
if(x == 38){
PY -= 1;
}
if(x == 39){
PX += 1;
}
if(x == 40){
PY += 1;
}
}
//detect collision
setInterval(function() {
if(PX > EX1 || PX + PW < EX1 + EW1 && PY + PH > EY1 + EH1 || PY + PH < EY1 + EH1){
window.alert("collision");
}
}, 1);
<html>
<head>
</head>
<body>
<canvas width="500px" height="500px" id="canvas" class="canvas">
</body>
</html>

Your formula for collision is wrong.
This problem is called Axis Aligned Bounding Box collision.
Two AABBs collide if their projections to each axis collide. In your 2-dimensinal case you have to consider the horizontal and vertical projections.
The projections are segments of 1-d space. Collision for those is very easy: if the start or the end of a segment is on the other they collide. Formally start2 <= start1 <= end2 or start2 <= end1 <= end2
In code:
intersects([p.x, p.x + p.width], [e.x, e.x + e.width]) && intersects([p.y, p.y + p.height], [e.y, e.y + e.height])
where
function intersects(seg1, seg2) {
return contains(seg1, seg2[0]) || contains(seg1, seg2[1])
}
function contains(segment, point) {
return segment[0] <= point && point <= segment[1]
}

How to set a delay in each penalty shot in HTML5 JS Canvas football penalty game

I am trying to make a simple football penalty game using HTML5/JS Canvas. The aim is to make a game where you control the goal keeper and you have three attempts to save the ball.
I have most of the functionality done, I have a score system and collision detection.
Currently I have a delay on the first attempt. I am however finding difficulty in adding a delay before the ball is shot into the goal in the second and third attempt.
I am using the method requestAnimationFrame() to paint my shapes on my canvas. If there is still attempts available, the ball is positioned to its original location but then there is no delay and fires the ball immediately.
Any advice ? Thanks!
<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8" />
<title>Football</title>
<style>
* { padding: 0; margin: 0; }
canvas { background: #a5bd7b; display: block; margin: 0 auto; }
</style>
</head>
<body>
<canvas id="myCanvas" width="300" height="250"></canvas>
<script>
var canvas = document.getElementById('myCanvas');
var ctx = canvas.getContext("2d");
//Sets the original position of the ball
var x = canvas.width/2;
var y = 50;
// Defines values that will be added to the position of x and y values
// List of possible values for the x position
var x_options = [3.5, 3, 2.5, 2, 1.5, 1, 0.5, 0, -0.5, -1, -1.5, -2, -2.5, -3, -3.5];
// Gets a random value from the x_options array
var dx = x_options[Math.floor(Math.random() * x_options.length)];
var dy = 5;
var ballRadius = 10;
// Defines the height and width of the goal
var goal_height = 40;
var goal_width = 200
// Defines the height, width and position of goalie
var goalieHeight = 20;
var goalieWidth = 40;
var goalieX = (canvas.width-goalieWidth)/2;
var goalieY = (canvas.height - goal_height) - 30;
// Set to false by default
var rightPressed = false;
var leftPressed = false;
var goalkeeper_blocked = 0;
var goalkeeper_missed = 0;
var attempts_left = 3;
var attempt1 = true;
var attempt2 = false;
var attempt3 = false;
var footBall = {
shapes : {
ball: function (){
ctx.beginPath();
ctx.arc(x, y, ballRadius, 0, Math.PI*2, false);
ctx.fillStyle = "red";
ctx.fill();
ctx.closePath();
},
goal : function (){
ctx.beginPath();
ctx.rect((canvas.width - goal_width) / 2 , canvas.height - goal_height, goal_width, goal_height);
ctx.strokeStyle = "#000000";
ctx.stroke();
ctx.closePath();
},
goalie : function(){
ctx.beginPath();
ctx.rect(goalieX, goalieY, goalieWidth, goalieHeight);
ctx.fillStyle = "#666666";
ctx.fill();
ctx.closePath();
},
score : function(){
ctx.font = "16px Arial";
ctx.fillStyle = "#ffffff";
ctx.fillText("Score: "+goalkeeper_blocked, 8, 20);
},
missed : function(){
ctx.font = "16px Arial";
ctx.fillStyle = "#ffffff";
ctx.fillText("Missed: "+goalkeeper_missed, 8, 40);
},
attempts : function(){
ctx.font = "16px Arial";
ctx.fillStyle = "#ffffff";
ctx.fillText("Attempts left: "+attempts_left, canvas.width-110, 20);
}
},
controls : {
keyDownHandler : function (e){
if(e.keyCode == 39) {
rightPressed = true;
}
else if(e.keyCode == 37) {
leftPressed = true;
}
},
keyUpHandler : function(e){
if(e.keyCode == 39) {
rightPressed = false;
}
else if(e.keyCode == 37) {
leftPressed = false;
}
}
},
calculateScore : function(){
if(goalkeeper_missed > goalkeeper_blocked){
alert("GAME OVER! YOU HAVE LOST!");
document.location.reload();
} else {
alert("GAME OVER! YOU HAVE WON!");
document.location.reload();
}
},
animateBall : function (){
// Sets a delay of 3 second before it shoots
setTimeout(function(){
x += dx;
y += dy;
}, 3000);
},
resetShapePositions : function(){
//Sets the original position of the ball
x = canvas.width/2;
y = 50;
// Sets a new shooting path
dx = x_options[Math.floor(Math.random() * x_options.length)];
dy = 5;
// Resets the goalie to the middle
goalieX = (canvas.width-goalieWidth)/2;
},
draw : function(){
// This ensures that the ball doesn't leave a trail
// Clears the canvas of this shape each frame
ctx.clearRect(0, 0, canvas.width, canvas.height);
// Draws shapes on the canvas
footBall.shapes.ball();
footBall.shapes.goal();
footBall.shapes.goalie();
footBall.shapes.score();
footBall.shapes.missed();
footBall.shapes.attempts();
// adds values to the balls x and y position every frame
footBall.animateBall();
// Ball hits the goal
if(y + dy > canvas.height - goal_height) {
attempts_left--;
goalkeeper_missed++;
if (!attempts_left){
footBall.calculateScore();
}
else {
footBall.resetShapePositions();
}
} // Ball saved by goalie
else if (x > goalieX && x < goalieX + goalieWidth && y + dy > goalieY - ballRadius){
attempts_left--;
goalkeeper_blocked++;
if (!attempts_left){
footBall.calculateScore();
}
else {
footBall.resetShapePositions();
}
}
// makes paddle move left and right and only within the canvas
if(rightPressed && goalieX < canvas.width-goalieWidth) {
goalieX += 7;
}
else if(leftPressed && goalieX > 0) {
goalieX -= 7;
}
requestAnimationFrame(footBall.draw);
}
}
footBall.draw();
// Defines what functions are fired when keydown or keyup event triggers
document.addEventListener("keydown", footBall.controls.keyDownHandler, false);
document.addEventListener("keyup", footBall.controls.keyUpHandler, false);
</script>
</body>
</html>

Add some properties to football that control if/when a shot is occuring:
// is a shot in progress?
isShooting:false,
// the time when next shot will start
nextShotTime:0,
// delay between shots
delayUntilNextShot:3000,
Then in the animation loop, use these properties to appropriately delay the next shot:
If isShooting, process the shot,
If not isShooting, see if the required delay has elapsed between shots. If yes, set isShooting=true,
When the goalie blocks or misses the shot, set isShooting=false and set nextShotTime=currentTime+delayUntilNextShot,
Example code and a Demo:
var canvas = document.getElementById('myCanvas');
var ctx = canvas.getContext("2d");
//Sets the original position of the ball
var x = canvas.width/2;
var y = 50;
// Defines values that will be added to the position of x and y values
// List of possible values for the x position
var x_options = [3.5, 3, 2.5, 2, 1.5, 1, 0.5, 0, -0.5, -1, -1.5, -2, -2.5, -3, -3.5];
// Gets a random value from the x_options array
var dx = x_options[Math.floor(Math.random() * x_options.length)];
var dy = 5;
var ballRadius = 10;
// Defines the height and width of the goal
var goal_height = 40;
var goal_width = 200
// Defines the height, width and position of goalie
var goalieHeight = 20;
var goalieWidth = 40;
var goalieX = (canvas.width-goalieWidth)/2;
var goalieY = (canvas.height - goal_height) - 30;
// Set to false by default
var rightPressed = false;
var leftPressed = false;
var goalkeeper_blocked = 0;
var goalkeeper_missed = 0;
var attempts_left = 3;
var attempt1 = true;
var attempt2 = false;
var attempt3 = false;
var footBall = {
// is a shot in progress
isShooting:false,
// time when next shot will run
nextShotTime:0,
// delay until next shot will run
delayUntilNextShot:3000,
shapes : {
ball: function (){
ctx.beginPath();
ctx.arc(x, y, ballRadius, 0, Math.PI*2, false);
ctx.fillStyle = "red";
ctx.fill();
ctx.closePath();
},
goal : function (){
ctx.beginPath();
ctx.rect((canvas.width - goal_width) / 2 , canvas.height - goal_height, goal_width, goal_height);
ctx.strokeStyle = "#000000";
ctx.stroke();
ctx.closePath();
},
goalie : function(){
ctx.beginPath();
ctx.rect(goalieX, goalieY, goalieWidth, goalieHeight);
ctx.fillStyle = "#666666";
ctx.fill();
ctx.closePath();
},
score : function(){
ctx.font = "16px Arial";
ctx.fillStyle = "#ffffff";
ctx.fillText("Score: "+goalkeeper_blocked, 8, 20);
},
missed : function(){
ctx.font = "16px Arial";
ctx.fillStyle = "#ffffff";
ctx.fillText("Missed: "+goalkeeper_missed, 8, 40);
},
attempts : function(){
ctx.font = "16px Arial";
ctx.fillStyle = "#ffffff";
ctx.fillText("Attempts left: "+attempts_left, canvas.width-110, 20);
}
},
controls : {
keyDownHandler : function (e){
if(e.keyCode == 39) {
rightPressed = true;
}
else if(e.keyCode == 37) {
leftPressed = true;
}
},
keyUpHandler : function(e){
if(e.keyCode == 39) {
rightPressed = false;
}
else if(e.keyCode == 37) {
leftPressed = false;
}
}
},
calculateScore : function(){
if(goalkeeper_missed > goalkeeper_blocked){
alert("GAME OVER! YOU HAVE LOST!");
document.location.reload();
} else {
alert("GAME OVER! YOU HAVE WON!");
document.location.reload();
}
},
resetShapePositions : function(){
//Sets the original position of the ball
x = canvas.width/2;
y = 50;
// Sets a new shooting path
dx = x_options[Math.floor(Math.random() * x_options.length)];
dy = 5;
// Resets the goalie to the middle
goalieX = (canvas.width-goalieWidth)/2;
},
drawField: function(){
// This ensures that the ball doesn't leave a trail
// Clears the canvas of this shape each frame
ctx.clearRect(0, 0, canvas.width, canvas.height);
// Draws shapes on the canvas
footBall.shapes.ball();
footBall.shapes.goal();
footBall.shapes.goalie();
footBall.shapes.score();
footBall.shapes.missed();
footBall.shapes.attempts();
},
draw : function(currentTime){
// makes paddle move left and right and only within the canvas
if(rightPressed && goalieX < canvas.width-goalieWidth) {
goalieX += 7;
}
else if(leftPressed && goalieX > 0) {
goalieX -= 7;
}
// draw the scene
footBall.drawField();
// delay until next shot time is due
if(!footBall.isShooting){
// time has elapsed, let's shoot again
if(currentTime>footBall.nextShotTime){
footBall.isShooting=true;
}else{
// time has not elapsed, just request another loop
requestAnimationFrame(footBall.draw);
return;
}
}
// adds values to the balls x and y position every frame
x += dx;
y += dy;
// Ball hits the goal
if(y + dy > canvas.height - goal_height) {
// end the shot
footBall.isShooting=false;
// delay the next shot
footBall.nextShotTime=currentTime+footBall.delayUntilNextShot;
attempts_left--;
goalkeeper_missed++;
if (!attempts_left){
footBall.calculateScore();
}
else {
footBall.resetShapePositions();
}
} // Ball saved by goalie
else if (x > goalieX && x < goalieX + goalieWidth && y + dy > goalieY - ballRadius){
// end the shot
footBall.isShooting=false;
// delay the next shot
footBall.nextShotTime=currentTime+footBall.delayUntilNextShot;
attempts_left--;
goalkeeper_blocked++;
if (!attempts_left){
footBall.calculateScore();
}
else {
footBall.resetShapePositions();
}
}
requestAnimationFrame(footBall.draw);
}
}
footBall.drawField();
footBall.nextShotTime=footBall.delayUntilNextShot;
requestAnimationFrame(footBall.draw);
// Defines what functions are fired when keydown or keyup event triggers
document.addEventListener("keydown", footBall.controls.keyDownHandler, false);
document.addEventListener("keyup", footBall.controls.keyUpHandler, false);
* { padding: 0; margin: 0; }
canvas { background: #a5bd7b; display: block; margin: 0 auto; }
<canvas id="myCanvas" width="300" height="250"></canvas>

How do you move a drawing in javascript up down right and left

I was wondering how to move the red ball right and left (I already did, but its not working) and also how to move it up and down.
<canvas id="canvas" width="480" height="320"></canvas>
var canvas = document.getElementById('canvas');
var ctx = canvas.getContext('2d');
var ball;
var obstacle;
var x = canvas.width / 2;
var y = canvas.height / 2;
var dx = 2;
var dy = -2;
var redballRadius = 10;
var ballRadius = 20;
var rightpressed = false;
var leftpressed = false;
var ballX = (canvas.width - redballDiameter) / 2;
var redballDiameter = redballRadius * 2;
function startGame() {
ctx.clearRect(0, 0, canvas.width, canvas.height);
ball = new drawBall(30, 30, 'red', 20, 10);
obstacle = new drawObstacle(40, 30, 'blue', 15, 10);
if (x + dx > canvas.width - ballRadius || x + dx < ballRadius) {
dx = -dx;
}
if (y + dy > canvas.height - ballRadius || y + dy < ballRadius) {
dy = -dy;
}
if(rightpressed && ballX < canvas.width-redballDiameter) {
ballX += 7;
}
else if(leftpressed && ballX > 0) {
ballX -= 7;
}
}
//keyboard controls
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;
}
}
function keyUpHandler(e) {
if(e.keyCode == 39) {
rightpressed = false;
}
else if (e.keyCode == 37) {
leftpressed = false;
}
}
function drawBall() {
ctx.beginPath();
ctx.arc(30, 30, 15, 0, 2 * Math.PI);
ctx.fillStyle = 'red';
ctx.fill();
ctx.closePath();
}
function drawObstacle() {
x += dx;
y += dy;
ctx.beginPath();
ctx.arc(x, y, 20, 10, 1 * Math.PI);
ctx.fillStyle = 'blue';
ctx.fill();
ctx.closePath();
}
setInterval(startGame, 10);
I am basically wondering how to move it up down right and left with the keys. Thanks

I took a look at your code. In your life cycle, you are calling drawBall, now sure what you are trying to do with the new there. anyways, I updated the function to use the ballX your key handling logic updates.
function drawBall() {
ctx.beginPath();
ctx.arc(ballX, 30, 15, 0, 2 * Math.PI);
ctx.fillStyle = 'red';
ctx.fill();
ctx.closePath();
}
here is the working code pen. http://codepen.io/poda/pen/aNPPEp

move a ball to up, down, right and left.
it would be better to use object than use global variable of x_pos and y_pos of ball
function drawBall() {
this.ball_x = 30;
this.ball_y = 30;
this.draw = function() {
ctx.beginPath();
ctx.arc(this.ball_x, this.ball_y, 15, 0, 2 * Math.PI);
ctx.fillStyle = 'red';
ctx.fill();
ctx.closePath();
},
this.move = function() {
if(rightpressed && this.ball_x < canvas.width-redballDiameter) {
this.ball_x += 5;
}
else if(leftpressed && this.ball_x > redballDiameter) {
this.ball_x -= 5;
}
else if(uppressed && this.ball_y > redballDiameter) {
this.ball_y -= 5;
}
else if(downpressed && this.ball_y < canvas.height - redballDiameter) {
this.ball_y += 5;
}
},
this.collision = function() {
//stuff
}
}
Here's a fiddle

moving canvas box with arrows

I've been trying to make a simple canvas box move with arrow keys. Here is the code: http://cssdeck.com/labs/stexplorer
And here also:
$(function() {
var n = 3;
var xD = 0;
var yD = 0;
//var move;
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
var ss = {
"x": 0,
"y": 0,
"width": 100,
"height": 75
};
function render() {
ctx.clearRect(0, 0, canvas.width, canvas.height);
ctx.beginPath();
ctx.rect(ss.x, ss.y, ss.width, ss.height);
ctx.lineWidth = 1;
ctx.strokeStyle = "black";
ctx.stroke();
}
function move() {
x = ss.x + (xD * n);
y = ss.y + (yD * n);
ss.x = x;
ss.y = y;
}
$(document).keydown(function(e) {
xD = e.which == 37 ? -1 : xD;
xD = e.which == 39 ? 1 : xD;
yD = e.which == 38 ? -1 : yD;
yD = e.which == 40 ? 1 : yD;
e.preventDefault();
});
$(document).keyup(function(e) {
xD = e.which == 37 ? 0 : xD;
xD = e.which == 39 ? 0 : xD;
yD = e.which == 38 ? 0 : yD;
yD = e.which == 40 ? 0 : yD;
e.preventDefault();
});
render();
setInterval(move, .01);
});
body {
margin: 0;
}
#canvas {
border: 1px solid #000000;
}
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<canvas id="canvas" width="300" height="200"></canvas>
This code should be doing the following:
Whenever I press an arrow key, the box should move
It would be great if I could make the canvas width = "100vw" and height = "100vh"

Your render method will only be fired initially, you should add it as the last line of the move method, so the canvas will render the new position after every move.
function move() {
x = ss.x + (xD * n);
y = ss.y + (yD * n);
ss.x = x;
ss.y = y;
render(); // add this line
}

Try this solution, click on result screen and than use keyboard arrow keys, also if this works for you mark my solution as answer, do post comment if you need anything else
var canvas;
var ctx;
var dx = 5;
var dy = 5;
var x = 150;
var y = 100;
var WIDTH = 300;
var HEIGHT = 200;
function circle(x,y,r) {
ctx.beginPath();
ctx.arc(x, y, r, 0, Math.PI*2, true);
ctx.fill();
}
function rect(x,y,w,h) {
ctx.beginPath();
ctx.rect(x,y,w,h);
ctx.closePath();
ctx.fill();
ctx.stroke();
}
function clear() {
ctx.clearRect(0, 0, WIDTH, HEIGHT);
}
function init() {
canvas = document.getElementById("canvas");
ctx = canvas.getContext("2d");
return setInterval(draw, 10);
}
function doKeyDown(evt){
switch (evt.keyCode) {
case 38: /* Up arrow was pressed */
if (y - dy > 0){
y -= dy;
}
break;
case 40: /* Down arrow was pressed */
if (y + dy < HEIGHT){
y += dy;
}
break;
case 37: /* Left arrow was pressed */
if (x - dx > 0){
x -= dx;
}
break;
case 39: /* Right arrow was pressed */
if (x + dx < WIDTH){
x += dx;
}
break;
}
}
function draw() {
clear();
ctx.fillStyle = "white";
ctx.strokeStyle = "black";
rect(0,0,WIDTH,HEIGHT);
ctx.fillStyle = "purple";
circle(x, y, 10);
}
init();
window.addEventListener('keydown',doKeyDown,true);
<!doctype html>
<html>
<head>
<meta charset="UTF-8" />
<title>Canvas Test</title>
</head>
<body>
<section>
<div>
<canvas id="canvas" width="300" height="200">
This text is displayed if your browser does not support HTML5 Canvas.
</canvas>
</div>