Question

我遇到了以下问题：我正在创建一个创建子弹的对象构造函数，当我尝试使用它时，“子弹”对象在控制台日志中返回undefined。我不知道什么是错的。

抱歉凌乱的代码和糟糕的英语。并提前感谢。编辑：如果你打算投票，请告诉我原因，以便我知道如何改进。

LinkList

var canvas, ctx, Player,players, intervalo,x,y, keyUp,keyDown,keyLeft,keyRight,rX,rY,rRadius,rAngle,hei, orbitals, Orbital, mouseX, mouseY, tiros, Bullet, bullets;
keyUp = 87; keyDown = 83; keyRight = 68; keyLeft = 65;
hei = 0;
test = 0; tiros = 0;
function load(){
	canvas = document.getElementById('box');
	ctx = canvas.getContext('2d');
	ctx.lineWidth = 3;
	function player(){
		this.x = canvas.width/2;
		this.y = canvas.height/2;
		this.speed = 2;
		this.width = 10;
		this.height = 10;
		
		this.up = false;
		this.down = false;
		this.left = false;
		this.right = false;
	}
	function orbital(){
		this.x = x;
		this.y = y;
		this.width = 3;
		this.height = 3;
		this.radius = 20;
		this.angle = hei;
		this.speed = 0;
	}
	Orbital = new Array();
	for (var i = 0;i < 10; i++){
		Orbital.push(new orbital())
		orbitals = Orbital[i];
		hei += 10;
		orbitals.angle = hei;
	}
	Player = new Array();
	Player.push(new player())
	players = Player[0];
	window.addEventListener("keydown", checkKeyDown, false);
	function checkKeyDown(e) {
		if (event.keyCode == keyUp){
			players.up = true;
			console.log("Up key is pressed");
		} else if (event.keyCode == keyDown){
			players.down = true;
			console.log("Down key is pressed");
		} else if (event.keyCode == keyLeft){
			players.left = true;
			console.log("Left key is pressed");
		} else if (event.keyCode == keyRight){
			players.right = true;
			console.log("Right key is pressed");
		}
	}
	window.addEventListener("keyup", checkKeyUp, false);	
	function checkKeyUp(e){
		if (event.keyCode == keyUp){
			players.up = false;
			console.log("Up key is released");
		} else if (event.keyCode == keyDown){
			players.down = false;
			console.log("Down key is released");
		} else if (event.keyCode == keyLeft){
			players.left = false;
			console.log("Left key is released");
		} else if (event.keyCode == keyRight){
			players.right = false;
			console.log("Right key is released");
		}
	}
	document.onmousemove = mouseMove;//Detectando posição do mouse;
	function mouseMove(e) {
		e = e || window.event
		mouseX = e.pageX;
		mouseY = e.pageY;
		document.getElementById('demo').innerHTML = mouseX + " " + mouseY;
	}
  //Here is where the bullet begins:
	function bullet(){ 
		this.x = players.x;
		this.y = players.y;
		this.width = 5;
		this.height = 5;
		this.speed = 20;
		var dX = mouseX - players.x;
		var dY = mouseY - players.y;
		var distance = Math.sqrt(dX*dX + dY*dY);
		this.speedX = (dX/distance) * 10;
		this.speedY = (dY/distance) * 10;
	}
	Bullet = new Array();
	canvas.onmousedown = function () {
        Bullet.push(new bullet()) 
		tiros++;
		bullets = Bullet[tiros];
		document.getElementById('demo2').innerHTML = tiros;
    };
}
function play(){
	intervalo = setInterval(animate, 1000/60);
}
function animate(){
	ctx.clearRect(0,0,canvas.width,canvas.height);// Os if's tem q estar em uma ordem específica onde o if que detecta o movimento tem q estar antes do if q detecta a colisão com o muro.
	//Key detection, that makes the player move.
	if (players.up){
		players.y -= players.speed;
	}
	if (players.down){
		players.y += players.speed;
	}
	if (players.right){
		players.x += players.speed;
	}
	if (players.left){
		players.x -= players.speed;
	}
	// End
	//Detecção de colisão no muro
	if (players.y < 50){
		players.y += players.speed;
	}
	if (players.y > canvas.height - players.height - 50){
		players.y -= players.speed;
	}
	if (players.x < 50){
		players.x += players.speed;
	}
	if (players.x > canvas.width - players.width - 50){
		players.x -= players.speed;
	}
	//end
	ctx.fillStyle = "brown";
	ctx.beginPath();
	ctx.moveTo(0,0);
	ctx.lineTo(50,50);
	ctx.moveTo(0,500);
	ctx.lineTo(50,450);
	ctx.moveTo(700,0);
	ctx.lineTo(650,50);
	ctx.moveTo(700,500);
	ctx.lineTo(650,450);
	ctx.strokeRect(50,50,600,400);
	ctx.stroke();
	angleToTurn = -Math.atan2((mouseX-15) - players.x, (mouseY-15) - players.y )*(180/Math.PI);//Pega a posição do players.x e do mouse para criar o angulo de movimento;
	for (var z = 0; z < Orbital.length; z++){
		ctx.fillStyle = "red";
		orbitals = Orbital[z];
		orbitals.angle = angleToTurn+85;
		orbitals.x = players.x+(orbitals.radius*Math.cos(orbitals.angle*(Math.PI/180)))+(players.width/2)-2;
		orbitals.y = players.y+(orbitals.radius*Math.sin(orbitals.angle*(Math.PI/180)))+(players.height/2)-2;
		if (orbitals.angle > 360){
			orbitals.angle = 0;
		}
		ctx.fillRect(orbitals.x,orbitals.y,orbitals.width,orbitals.height);
	}
    //Here is the part that returns undefined at the console log
	if (tiros >= 1){
		bullets.x += bullets.speedX;
		bullets.y += bullets.speedY;
		document.getElementById('demo2').innerHTML = "if";
		ctx.fillRect(bullets.x,bullets.y,bullets.width,bullets.height);
	}
	ctx.fillStyle = "black";
	ctx.fillRect(players.x,players.y,players.width,players.height);
}

Answer 1

问题似乎是tiros在被使用之前递增，应该在之后。尝试：

    canvas.onmousedown = function () {
        Bullet.push(new bullet()) 
        bullets = Bullet[tiros++];
        document.getElementById('demo2').innerHTML = tiros;
    };

函数对象返回undefined

1 个答案: