<!DOCTYPE html>
<html>
<head>
<title></title>
</head>
<body>
<canvas id = "canvas"></canvas></p> <p> <script>
var Loading = function (canvas, options) {
this.canvas = document.getElementById(canvas);
this.options = options;
};</p> <p> Loading.prototype = {
constructor: Loading,
show: function () {
var canvas = this.canvas,
begin = this.options.begin,
old = this.options.old,
lineWidth = this.options.lineWidth,
canvasCenter = {x: canvas.width / 2, y: canvas.height / 2},
ctx = canvas.getContext("2d"),
color = this.options.color,
num = this.options.num,
angle = 0,
lineCap = this.options.lineCap,
CONST_PI = Math.PI * (360 / num) / 180;
window.timer = setInterval(function () {
ctx.clearRect(0, 0, canvas.width, canvas.height);
for (var i = 0; i < num; i += 1) {
ctx.beginPath();
ctx.strokeStyle = color[num - 1 - i];
ctx.lineWidth = lineWidth;
ctx.lineCap= lineCap;
ctx.moveTo(canvasCenter.x + Math.cos(CONST_PI * i + angle) * begin, canvasCenter.y + Math.sin(CONST_PI * i + angle) * begin);
ctx.lineTo(canvasCenter.x + Math.cos(CONST_PI * i + angle) * old, canvasCenter.y + Math.sin(CONST_PI * i + angle) * old);
ctx.stroke();
ctx.closePath();
}
angle += CONST_PI;
console.log(angle)
},50);
},
hide: function () {
clearInterval(window.timer);
}
};</p> <p> (function () {
var options = {
num : 8,
begin: 20,
old: 40,
lineWidth: 10,
lineCap: "round",
color: ["rgb(0, 0, 0)", "rgb(20, 20, 20)","rgb(40, 40, 40)", "rgb(60, 60, 60)","rgb(80, 80, 80)", "rgb(100, 100, 100)", "rgb(120, 120, 120)", "rgb(140, 140, 140)"]
};
var loading = new Loading("canvas", options);
loading.show();
}());
</script>
</body>
</html>
效果图：