影子的大小怎么会每 n 秒改变一次？我猜你必须不断地创建一个新的圈子并消除以前的圈子？这将如何完成？还有，有没有更好的办法？
function main() {
var canvas = document.getElementsByTagName("CANVAS")[0],
ctx = canvas.getContext("2d");
canvas.width = window.innerWidth;
canvas.height = document.documentElement.scrollHeight;
var cW = canvas.width,
cH = canvas.height;
ctx.fillStyle = "#000";
ctx.fillRect(0, 0, cW, cH);
ctx.fill();
ctx.beginPath();
ctx.fillStyle = "#FFF";
ctx.shadowBlur = 5;
ctx.shadowColor = "#FFF";
ctx.arc(cW/2, cH/2, 50, 0, 2 * Math.PI, false);
ctx.fill();
ctx.closePath();
}
window.addEventListener("load", main);<!DOCTYPE html>
<html>
<head>
<meta charset="utf-8">
<meta name="viewport" content="width=device-width">
<title>JS Bin</title>
</head>
<body>
<canvas></canvas>
</body>
</html>最佳答案
创建一个 setInterval 和一个颜色数组。使用 Math.random 随机选择任何颜色。
修改 main 函数以接受颜色作为两个参数。
function main(bckColor, circleColor) {
var canvas = document.getElementsByTagName("CANVAS")[0],
ctx = canvas.getContext("2d");
if (canvas.height) {
canvas.height = 0;
}
canvas.width = window.innerWidth;
canvas.height = document.documentElement.scrollHeight;
var cW = canvas.width,
cH = canvas.height;
ctx.fillStyle = bckColor || "#000";
//ctx.fillStyle = "red" ;
ctx.fillRect(0, 0, cW, cH);
ctx.fill();
ctx.beginPath();
ctx.fillStyle = circleColor || "#FFF";
ctx.shadowBlur = 5;
ctx.shadowColor = "#FFF";
ctx.arc(cW / 2, cH / 2, 50, 0, 2 * Math.PI, false);
ctx.fill();
ctx.closePath();
}
var colorArray = ['red', 'green', 'yellow', 'blue', 'pink', 'brown', 'orange']
var changeColor = setInterval(function() {
let bckColor = colorArray[Math.floor(Math.random() * 7 + 1)];
let circleColor = colorArray[Math.floor(Math.random() * 7 + 1)];
main(bckColor, circleColor)
}, 2000)
window.addEventListener("load", main);<canvas></canvas>关于javascript - 如何每隔 n 秒更改 Canvas 上圆圈的颜色？，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/49992994/