<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<meta name="viewport" content="width=device-width, initial-scale=1.0">
<meta http-equiv="X-UA-Compatible" content="ie=edge">
<title>canvas</title>
</head>
<body>
<di class="can">
<h1 onclick="drawstar()">canvas click to draw star</h1>
<canvas id="canvas" width=300 height=300></canvas>
</di>
</body>
<script>
function drawstar() {
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
function drawStar(cx, cy, spikes, outerRadius, innerRadius) {
var rot = Math.PI / 2 * 3;
var x = cx;
var y = cy;
var step = Math.PI / spikes;
ctx.beginPath();
ctx.moveTo(cx, cy - outerRadius)
for (i = 0; i < spikes; i++) {
x = cx + Math.cos(rot) * outerRadius;
y = cy + Math.sin(rot) * outerRadius;
ctx.lineTo(x, y)
rot += step
x = cx + Math.cos(rot) * innerRadius;
y = cy + Math.sin(rot) * innerRadius;
ctx.lineTo(x, y)
rot += step
}
ctx.lineTo(cx, cy - outerRadius);
ctx.closePath();
ctx.lineWidth = 5;
ctx.strokeStyle = 'blue';
ctx.stroke();
ctx.fillStyle = 'skyblue';
ctx.fill();
}
drawStar(100, 100, 5, 30, 15);
}
</script>
</html>