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我在网上查到了这个平台的游戏，我修改了一点：复制一个JavaScript内随机多个对象进行循环
<canvas id="canvas" widht=1000 height=400></canvas>
<script>
(function() {
var requestAnimationFrame = window.requestAnimationFrame || window.mozRequestAnimationFrame || window.webkitRequestAnimationFrame || window.msRequestAnimationFrame;
window.requestAnimationFrame = requestAnimationFrame;
})();
var canvas = document.getElementById("canvas"),
ctx = canvas.getContext("2d"),
width = 1000,
height = 400,
player = {
x: width/2,
y: height - 15,
width: 5,
height: 5,
speed: 3,
velX: 0,
velY: 0,
jumping: false,
grounded: false
},
keys = [],
friction = 0.8,
gravity = 0.3;
var boxes = [];
// dimensions
a = Math.floor((Math.random() * 20) + 1);
for (i = 0; i < a; i++) {
random1 = Math.floor((Math.random() * 1000) + 1);
random2 = Math.floor((Math.random() * 400) + 1);
random3 = Math.floor((Math.random() * 200) + 1);
random4 = Math.floor((Math.random() * 200) + 1);
boxes.push({
x: random1,
y: random2,
width: random3,
height: random4
}
boxes.push({
x: 0,
y: 0,
width: 10,
height: height
});
boxes.push({
x: 0,
y: height - 2,
width: width,
height: 50
});
boxes.push({
x: width - 10,
y: 0,
width: 50,
height: height
});
canvas.width = width;
canvas.height = height;
function update() {
// check keys
if (keys[38] || keys[32]) {
// up arrow or space
if (!player.jumping && player.grounded) {
player.jumping = true;
player.grounded = false;
player.velY = -player.speed * 2;
}
}
if (keys[39]) {
// right arrow
if (player.velX < player.speed) {
player.velX++;
}
}
if (keys[37]) {
// left arrow
if (player.velX > -player.speed) {
player.velX--;
}
}
player.velX *= friction;
player.velY += gravity;
ctx.clearRect(0, 0, width, height);
ctx.fillStyle = "black";
ctx.beginPath();
player.grounded = false;
for (var i = 0; i < boxes.length; i++) {
ctx.rect(boxes[i].x, boxes[i].y, boxes[i].width, boxes[i].height);
var dir = colCheck(player, boxes[i]);
if (dir === "l" || dir === "r") {
player.velX = 0;
player.jumping = false;
} else if (dir === "b") {
player.grounded = true;
player.jumping = false;
} else if (dir === "t") {
player.velY *= -1;
}
}
if(player.grounded){
player.velY = 0;
}
player.x += player.velX;
player.y += player.velY;
ctx.fill();
ctx.fillStyle = "red";
ctx.fillRect(player.x, player.y, player.width, player.height);
requestAnimationFrame(update);
}
function colCheck(shapeA, shapeB) {
// get the vectors to check against
var vX = (shapeA.x + (shapeA.width/2)) - (shapeB.x + (shapeB.width/2)),
vY = (shapeA.y + (shapeA.height/2)) - (shapeB.y + (shapeB.height/2)),
// add the half widths and half heights of the objects
hWidths = (shapeA.width/2) + (shapeB.width/2),
hHeights = (shapeA.height/2) + (shapeB.height/2),
colDir = null;
// if the x and y vector are less than the half width or half height, they we must be inside the object, causing a collision
if (Math.abs(vX) < hWidths && Math.abs(vY) < hHeights) {
// figures out on which side we are colliding (top, bottom, left, or right)
var oX = hWidths - Math.abs(vX),
oY = hHeights - Math.abs(vY);
if (oX >= oY) {
if (vY > 0) {
colDir = "t";
shapeA.y += oY;
} else {
colDir = "b";
shapeA.y -= oY;
}
} else {
if (vX > 0) {
colDir = "l";
shapeA.x += oX;
} else {
colDir = "r";
shapeA.x -= oX;
}
}
}
return colDir;
}
document.body.addEventListener("keydown", function (e) {
keys[e.keyCode] = true;
});
document.body.addEventListener("keyup", function (e) {
keys[e.keyCode] = false;
});
window.addEventListener("load", function() {
update();
});
</script>的问题是在for循环时，我想创建具有随机宽度，高度，位置的多个框但是不起作用。我怎么能这样做？