Question

我在互联网上找到了这个平台游戏，我对它进行了一些修改：

＆＃13;

<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>

＆＃13;

当我想要创建具有随机宽度，高度，位置但不起作用的多个框时，问题出现在for循环中。我怎么能这样做？

Answer 1

在您的代码中有两个语法错误。第一个是你没有关闭循环，第二个是内循环第一次推动操作没有正确关闭。我有更新代码。

＆＃13;

(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();
});

＆＃13;

<canvas id="canvas" widht=1000 height=400></canvas>

＆＃13;

在javascript for循环中随机复制多个对象

1 个答案: