I am new to javascript and to programming in general so don't assume I know a lot.
I am creating a simple html5 javascript game where vehicles on a highway are coming down towards you (represented by canvas rectangles). I am creating the vehicle spawning and movement at the moment. My goal is to have the vehicles spawn and come down with a constant space in between them regardless of what speed they are going.
What I have works except when any lag occurs and when the speed variable gets set to around the numbers four and under. I did some research and I believe this is because setTimeout doesn't take lag into account. Since I am new I don't know many of the functions, I have no clue on how to fix this and I can't find a solution online.
You can see a working demo of my code here - mess with opening tabs and other lag causing processes and you can try setting the speed variable to a number below 5 and you'll see where i'm coming from. Any help is appreciated.
<!DOCTYPE html>
<html>
<body>
<canvas id="ctx" width="480" height="320" style="border:1px solid #000000;"></canvas>
<script>
var ctx = document.getElementById("ctx").getContext("2d");
function setIntervalX(callback, delay, repetitions) {
var x = 0;
var intervalID = window.setInterval(function () {
callback();
if (++x === repetitions) {
window.clearInterval(intervalID);
}
}, delay);
}
var speed = 50
function game() {
var yAxis
var selectType = Math.floor((Math.random()*6)+1)
switch (selectType){
case 1: //semi
case 2:
yAxis = -80
var lane = Math.floor((Math.random()*3)+1)
switch (lane)
{
case 1: //left lane
setIntervalX(function () {
ctx.fillStyle = "white";
ctx.fillRect(200,yAxis,15,80);
yAxis = yAxis + 2
ctx.fillStyle = "black";
ctx.fillRect(200,yAxis,15,80);
}, speed, 400);
break;
case 2: //middle lane
setIntervalX(function () {
ctx.fillStyle = "white";
ctx.fillRect(230,yAxis,15,80);
yAxis = yAxis + 2
ctx.fillStyle = "black";
ctx.fillRect(230,yAxis,15,80);
}, speed, 400);
break;
case 3: //right lane
setIntervalX(function () {
ctx.fillStyle = "white";
ctx.fillRect(260,yAxis,15,80);
yAxis = yAxis + 2
ctx.fillStyle = "black";
ctx.fillRect(260,yAxis,15,80);
}, speed, 400);
break;
}
setTimeout(function() {game()}, speed * 80)
break;
case 3: //bike
yAxis = -10
var lane = Math.floor((Math.random()*3)+1)
switch (lane)
{
case 1: //left lane
setIntervalX(function () {
ctx.fillStyle = "white";
ctx.fillRect(200,yAxis,10,10);
yAxis = yAxis + 2
ctx.fillStyle = "black";
ctx.fillRect(200,yAxis,10,10);
}, speed, 400);
break;
case 2: //middle lane
setIntervalX(function () {
ctx.fillStyle = "white";
ctx.fillRect(230,yAxis,10,10);
yAxis = yAxis + 2
ctx.fillStyle = "black";
ctx.fillRect(230,yAxis,10,10);
}, speed, 400);
break;
case 3: //right lane
setIntervalX(function () {
ctx.fillStyle = "white";
ctx.fillRect(260,yAxis,10,10);
yAxis = yAxis + 2
ctx.fillStyle = "black";
ctx.fillRect(260,yAxis,10,10);
}, speed, 400);
break;
}
setTimeout(function() {game()}, speed * 45)
break;
case 4: //car
case 5:
case 6:
yAxis = -20
var lane = Math.floor((Math.random()*3)+1)
switch (lane)
{
case 1: //left lane
setIntervalX(function () {
ctx.fillStyle = "white";
ctx.fillRect(200,yAxis,10,20);
yAxis = yAxis + 2
ctx.fillStyle = "black";
ctx.fillRect(200,yAxis,10,20);
}, speed, 400);
break;
case 2: //middle lane
setIntervalX(function () {
ctx.fillStyle = "white";
ctx.fillRect(230,yAxis,10,20);
yAxis = yAxis + 2
ctx.fillStyle = "black";
ctx.fillRect(230,yAxis,10,20);
}, speed, 400);
break;
case 3: //right lane
setIntervalX(function () {
ctx.fillStyle = "white";
ctx.fillRect(260,yAxis,10,20);
yAxis = yAxis + 2
ctx.fillStyle = "black";
ctx.fillRect(260,yAxis,10,20);
}, speed, 400);
break;
}
setTimeout(function() {game()}, speed * 50)
break;}
}
game()
</script>
</body>
</html>
You should only have 1 main setInterval that updates everything.
Lag shouldn't be an issue, especially with a project of this size.