Web Front-endJS TutorialNative js combined with html5 to create a simple jumping ball for the little flying dragon_javascript skillsNative js combined with html5 to create a simple jumping ball for the little flying dragon_javascript skills
Demo address: http://runjs.cn/detail/yjpvqhal
html code
<html>
<head>
<meta charset="utf-8"/>
<title>小飞龙的跳球</title>
</head>
<body onload="init()">
<canvas id="game" width="400" height="400" style="border:1px solid #c3c3c3">
你的游览器不支持html5的画布元素，请升级到IE9+或使用firefox、chrome这类高级的智能游览器！
</canvas>
<script>
var canvas = document.getElementById('game');
var ctx = canvas.getContext('2d');
var grad;
//盒子的起始位置和大小以及球的半径
var box = {x:20,y:20,w:350,h:350,r:20};
//球的中心位置和偏移位置
var inbox = {//box内的限制范围
bx:(box.w+box.x-box.r),
by:(box.h+box.y-box.r),
ix:box.x+(box.r*2),
iy:box.y+(box.r*2)
};
//球的初始位置和变化位置
var ball = {x:50,y:50,vx:4,vy:8};
var img = new Image();
img.src = 'images/qiuqiu.png';
var hue = [[255,0,0],[255,255,0],[0,255,0],[0,255,255],[0,0,255],[255,0,0]];
function init(){
grad = ctx.createLinearGradient(box.x,box.y,box.w,box.h);
for(var i=0;i<hue.length;i++){
var color = 'rgb('+hue[i][0]+','+hue[i][1]+','+hue[i][2]+')';
grad.addColorStop(i/hue.length,color);
}
ctx.lineWidth = box.r;
ctx.fillStyle = 'rgb(200,0,50)';
ctx.fillStyle = grad;
moveBall();
setInterval(moveBall,50);
}
//碰撞检测并重新确定球的位置
function moveBallEndCheck(){
var nx = ball.x + ball.vx;
var ny = ball.y + ball.vy;
if(nx > inbox.bx){//当前x大于上边框边界
ball.vx = -ball.vx;//球的变化x坐标当前当前变化x坐标的负数
nx = inbox.bx;//当前位置为上边框的位置
}
if(nx < inbox.ix){//当前位置小于下边框
nx = inbox.ix;//当前位置为下边框的x
ball.vx = -ball.vx;//球的变化x坐标翻转取负
}
if(ny > inbox.by){
ny = inbox.by;
ball.vy = -ball.vy;
}
if(ny < inbox.iy){
ny = inbox.iy;
ball.vy = -ball.vy;
}
ball.x = nx;
ball.y = ny;
}
function moveBall(){
ctx.clearRect(box.x,box.y,box.w,box.h);
moveBallEndCheck();
ctx.beginPath();
//console.log(ball.x+"\t"+ball.y+"\t"+ball.vx+"\t"+ball.vy+"\t"+(ball.x-box.r)+"\t"+(ball.y-box.r));
ctx.drawImage(img,(ball.x-box.r),(ball.y-box.r));
ctx.fillRect(box.x,box.y,box.r,box.h);
ctx.fillRect((box.x+box.w-box.r),box.y,box.r,box.h);
ctx.fillRect(box.x,box.y,box.w,box.r);
ctx.fillRect(box.x,(box.y+box.h-box.r),box.w,box.r);
ctx.closePath();
ctx.fill();
}
</script>
</body>
</html>
Demo pictures
The above is the entire code of this article, I hope you all like it.
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