Question

我一直在使用JavaScript来关注W3School的HTML5游戏开发教程来创建一个相当简单的游戏。

代码有效，但我想在绿色块碰撞大红色块时将其更改为透明。以下是我的代码：

<!DOCTYPE html>
<html>
<head>
<meta name="viewport" content="width=device-width, initial-scale=1.0"/>
<style>
canvas {
    border:1px solid #d3d3d3;
    background-color: #f1f1f1;
}
</style>
</head>
<body onload="startGame()">
<script>
var score = 0;
var myGamePiece;
var myObstacles = [];
var myScore;

function startGame() {
    myGamePiece = new component(30, 30, "red", 10, 120);
    myScore = new component("30px", "Consolas", "black", 280, 40, "text");
    myGameArea.start();
}

var myGameArea = {
    canvas : document.createElement("canvas"),
    start : function() {
        this.canvas.width = 480;
        this.canvas.height = 270;
        this.context = this.canvas.getContext("2d");
        document.body.insertBefore(this.canvas, document.body.childNodes[0]);
        this.frameNo = 0;
        this.interval = setInterval(updateGameArea, 20);
        },
    clear : function() {
        this.context.clearRect(0, 0, this.canvas.width, this.canvas.height);
    }
}

function component(width, height, color, x, y, type) {
    this.type = type;
    this.width = width;
    this.height = height;
    this.speedX = 0;
    this.speedY = 0;
    this.x = x;
    this.y = y;
    this.update = function() {
        ctx = myGameArea.context;
        if (this.type == "text") {
            ctx.font = this.width + " " + this.height;
            ctx.fillStyle = color;
            ctx.fillText(this.text, this.x, this.y);
        } else {
            ctx.fillStyle = color;
            ctx.fillRect(this.x, this.y, this.width, this.height);
        }
    }
    
    this.newPos = function() {
        this.x += this.speedX;
        this.y += this.speedY;
    }
    this.crashWith = function(otherobj) {
        var myleft = this.x;
        var myright = this.x + (this.width);
        var mytop = this.y;
        var mybottom = this.y + (this.height);
        var otherleft = otherobj.x;
        var otherright = otherobj.x + (otherobj.width);
        var othertop = otherobj.y;
        var otherbottom = otherobj.y + (otherobj.height);
        var crash = true;
        if ((mybottom < othertop) || (mytop > otherbottom) || (myright < otherleft) || (myleft > otherright)) {
            crash = false;
        }
        return crash;
    }
}

function updateGameArea() {
    var x, height, gap, minHeight, maxHeight, minGap, maxGap;
    for (i = 0; i < myObstacles.length; i += 1) {
        if (myGamePiece.crashWith(myObstacles[i])) {
            score += 1;
     

        }
    }
    myGameArea.clear();
    myGameArea.frameNo += 1;
    if (myGameArea.frameNo == 1 || everyinterval(300)) {
        x = myGameArea.canvas.width;
        y = myGameArea.canvas.height;
        y = Math.floor(Math.random() * y);  
        myObstacles.push(new component(10, 10, "green", x, y));
       
    }
    for (i = 0; i < myObstacles.length; i += 1) {
        myObstacles[i].speedX = -1;
        myObstacles[i].newPos();
        myObstacles[i].update();
    }
    myScore.text="SCORE: " + score;
    myScore.update();
    myGamePiece.newPos();
    myGamePiece.update();
}

function everyinterval(n) {
    if ((myGameArea.frameNo / n) % 1 == 0) {return true;}
    return false;
}

function moveup() {
    myGamePiece.speedY = -1;
}

function movedown() {
    myGamePiece.speedY = 1;
}

function moveleft() {
    myGamePiece.speedX = -1;
}

function moveright() {
    myGamePiece.speedX = 1;
}

function clearmove() {
    myGamePiece.speedX = 0;
    myGamePiece.speedY = 0;
}

</script>
<div style="text-align:center;width:480px;">
  <button onmousedown="moveup()" onmouseup="clearmove()" ontouchstart="moveup()">UP</button><br><br>
  <button onmousedown="moveleft()" onmouseup="clearmove()" ontouchstart="moveleft()">LEFT</button>
  <button onmousedown="moveright()" onmouseup="clearmove()" ontouchstart="moveright()">RIGHT</button><br><br>
  <button onmousedown="movedown()" onmouseup="clearmove()" ontouchstart="movedown()">DOWN</button>
</div>

<p>The score will count one point for each frame you manage to "stay alive".</p>
</body>
</html>

我试过写一个类似于更新函数的changeColor（）函数，但是用ctx.fillStyle =“rgba（0,0,0,0）”;

我已经坚持了很长时间。任何形式的援助将不胜感激。

Answer 1

您需要向this.color函数构造函数添加component属性（color中的this.color函数中的update()必须为color。然后只需更改myObstacles [i]的{{1}}属性，当你迭代它们并检测到碰撞时（＆＃34;透明＆＃34;有效，我相信）。

Here是一个小提琴。祝你好运！

尝试在JavaScript

1 个答案: