给大家分享一个Canvas绘制的转盘抽奖，点击开关开始转动时，转盘开始转动，转盘停止时指针指向的区域即为抽中的奖品，并显示在转盘中间，效果图如下：
动画实的代码如下：
<!DOCTYPE html>
<html>
<head>
<style>
canvas {
background: #eee;
}
</style>
<title>Canvas绘制抽奖转盘</title>
<script>
window.onload = function () {
var canvas = document.getElementById("canvas");
var cobj = canvas.getContext("2d");
var btn = document.getElementById("btn");
var num = Math.PI / 180;
cobj.translate(250, 250);
var colorArr = ["#24a274", "#2a70a6", "#6d56c3", "#b23880", "#7a9a36", "#b48548", "#397839", "#89489c"];
var textArr = ["js", "html", "css", "php", "mysql", "node", "flutter", "java"];
var angle = 0;
btn.onclick = function () {
location.reload();
};
var step = 10 + 10 * Math.random();
var t = setInterval(function () {
if (step <= 0.3) {
clearInterval(t);
var num1 = Math.ceil(angle / 45);
var con = textArr[textArr.length - num1];
cobj.font = "18px sans-serif";
cobj.textAlign = "center";
cobj.fillText(con, 0, 0);
} else {
if (angle >= 360) {
angle = 0;
}
step *= 0.95;
angle += step;
cobj.clearRect(-200, -200, 500, 500);
cobj.beginPath();
cobj.lineWidth = 5;
cobj.moveTo(135, 0);
cobj.lineTo(150, 0);
cobj.stroke();
cobj.lineWidth = 2;
cobj.save();
cobj.rotate(angle * num);
for (var i = 1; i <= 8; i++) {
cobj.beginPath();
cobj.moveTo(0, 0);
cobj.fillStyle = colorArr[i - 1];
cobj.arc(0, 0, 130, (i - 1) * 45 * num, i * 45 * num);
cobj.closePath();
cobj.stroke();
cobj.fill();
}
cobj.beginPath();
cobj.fillStyle = "#fff";
cobj.arc(0, 0, 60, 0, 2 * Math.PI);
cobj.fill();
for (var i = 0; i < 8; i++) {
cobj.save();
cobj.beginPath();
cobj.rotate((i * 45 + 20) * num);
cobj.fillStyle = "#222";
cobj.font = "18px sans-serif";
cobj.fillText(textArr[i], 75, 0);
cobj.restore();
}
cobj.restore();
}
}, 60)
}
</script>
</head>
<body>
<canvas id="canvas" width=500 height=500></canvas>
<input type="button" value="开始" id="btn" />
</body>
</html>
