本文实例讲述了基于canvas实现的钟摆效果。分享给大家供大家参考，具体如下：
运行效果截图如下：
具体代码如下：
<!DOCTYPE html>
<html>
<head>
<title>demo</title>
<style type="text/css">
body {
margin:0; padding:0;
}
#canvas {
border:2px solid gray; box-shadow:0px 0px 2px 2px #494949;
}
</style>
</head>
<body>
<canvas id="canvas" width="500px" height="500px"></canvas>
<script type="text/javascript">
var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
var r = 250;
var colorList = "abcdefABCDEF0123456789".split("");
var colorListLength = colorList.length;
var color = function() {
var _color = "#";
for(var i=0; i<6; i++) {
_color += colorList[Math.round(Math.random()*colorListLength)];
}
return _color;
};
var createArc = function(attrs) {
ctx.save();
ctx.beginPath();
ctx.fillStyle = attrs.color || color();
ctx.arc(attrs.x, attrs.y, attrs.r, 0, Math.PI*2);
ctx.closePath();
ctx.fill();
ctx.restore();
};
var createLine = function(from, to) {
ctx.save();
ctx.beginPath();
ctx.moveTo(from.x, from.y);
ctx.lineTo(to.x, to.y);
ctx.stroke();
ctx.closePath();
ctx.restore();
}
var createAll = function(to) {
createArc({x: 250, y: 0, r: 10, color: "black"});
createArc({x: to.x, y: to.y, r: 20, color: "black"});
createLine({x: 250, y: 0}, {x: to.x, y: to.y});
};
var minAngle = 0;
var maxAngle = Math.PI;
var addAngle = Math.PI/24;
var angle = minAngle;
var mode = "left";
var interval = setInterval(function() {
var y = Math.sin(angle)*r+200;
var x = Math.cos(angle)*r+250;
switch(mode) {
case "left":
ctx.clearRect(0, 0, 500, 500);
createAll({x: x, y: y});
angle += addAngle;
if(angle > maxAngle) {
mode = "right";
angle -= addAngle;
return;
}
break;
case "right":
ctx.clearRect(0, 0, 500, 500);
createAll({x: x, y: y});
angle -= addAngle;
if(angle < minAngle) {
mode = "default";
angle += addAngle;
return;
}
break;
case "default":
createAll({x: x, y: y});
angle += addAngle;
if(angle > maxAngle) {
mode = "left";
angle = minAngle;
return;
}
break;
}
}, 50);
</script>
</body>
</html>
更多关于js特效相关内容感兴趣的读者可查看本站专题：《jQuery动画与特效用法总结》及《jQuery常见经典特效汇总》
希望本文所述对大家JavaScript程序设计有所帮助。