canvas实现
<!DOCTYPE html>
<html>
<body>
<canvas id="countdownCanvas" width="200" height="200"></canvas>
<script>
const canvas = document.getElementById('countdownCanvas');
const ctx = canvas.getContext('2d');
const centerX = canvas.width / 2;
const centerY = canvas.height / 2;
const radius = 70;
let count = 5; // 倒计时5秒
let angle = 0; // 起始角度
let timer; // 计时器
function drawCircle(count) {
ctx.beginPath();
var endAngle = (Math.PI * 2) / 5 * count; // 每次调用增加约2度
ctx.arc(centerX, centerY, radius, 0, endAngle);
var g = ctx.createLinearGradient(-0.5 * Math.PI, count, 180, 0); //创建渐变对象 渐变开始点和渐变结束点
g.addColorStop(0, '#17d1ff'); //添加颜色点
g.addColorStop(1, '#209cff'); //添加颜色点
ctx.strokeStyle = g; //使用渐变对象作为圆环的颜色
ctx.lineWidth = 10;
ctx.stroke();
}
function drawCountdown() {
ctx.clearRect(0, 0, canvas.width, canvas.height);
countdownTimer = setInterval(function() {
if (count > 0) {
count--;
console.log("倒计时：" + count)
drawCircle(5 - count);
} else {
clearInterval(countdownTimer);
}
}, 1000);
}
drawCountdown()// 开始倒计时
</script>
</body>
</html>
html5
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