html canvas 化一個彩虹
阿新 • • 發佈：2018-11-01
</<!doctype html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
</head>
<body>
123
<canvas id="canvas">該瀏覽器不支援canvas，請更換瀏覽器後檢視</canvas>
<script>
window.onload=function () {
var canvas = document.getElementById('canvas');
var a = 1000;
var a2 = a*2;
var aa2 = a/2;
canvas.width=a2;
canvas.height=a;
var sc = canvas.getContext("2d");
sc.lineWidth = 5;
sc.strokeStyle = "#00ffff";
for(var i = 300;i<=aa2;i+=100){
sc.beginPath();
sc.arc(a,a,i,0,0.5*Math.PI,true);
sc.stroke();
}
}
</script>
</body>
</html>
這也不能叫彩虹，叫橋洞吧