用两种方法实现一个点绕着另一个点旋转
用两种方法实现一个点绕着另一个点旋转
CSS3方法
@keyframes,animation, transform三样便可以搞定
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
<style type="text/css">
#center {
width:10px;
height: 10px;
border-radius: 5px;
background: #000;
position: relative;
margin: 200px auto;
}
#dot {
width: 10px;
height: 10px;
background: red;
position: absolute;
border-radius: 5px;
left: 200px;
top: 0;
-o-transform: rotate(90deg);
-moz-transform: rotate(90deg);
-webkit-transform: rotate(90deg);
-ms-transform: rotate(90deg);
transform: rotate(90deg);
-o-transform-origin: -2000%;
-webkit-transform-origin: -2000%;
-moz-transform-origin: -2000%;
-ms-transform-origin: -2000%;
transform-origin: -2000%;
animation: rot 3s linear 0s infinite;
-o-animation: rot 3s linear 0s infinite;
-ms-animation: rot 3s linear 0s infinite;
-webkit-animation: rot 3s linear 0s infinite;
-moz-animation: rot 3s linear 0s infinite;
}
@keyframes rot {
from{
transform: rotate(0deg);
}
to{
transform: rotate(360deg);
}
}
@-o-keyframes rot {
from{
-o-transform: rotate(0deg);
}
to{
-o-transform: rotate(360deg);
}
}
@-webkit-keyframes rot {
from{
-webkit-transform: rotate(0deg);
}
to{
-webkit-transform: rotate(360deg);
}
}
@-moz-keyframes rot {
from{
-moz-transform: rotate(0deg);
}
to{
-moz-transform: rotate(360deg);
}
}
@-ms-keyframes rot {
from{
-ms-transform: rotate(0deg);
}
to{
-ms-transform: rotate(360deg);
}
}
</style>
</head>
<body>
<div id="center">
<div id="dot"></div>
</div>
</body>
</html>
javascript
Math.cos(), Math.sin(),这两个函数的参数都是弧度，所以可以用 Math.PI * 2/360 将角度转化成弧度。
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
<style type="text/css">
#center {
width:10px;
height: 10px;
border-radius: 5px;
background: #000;
position: relative;
margin: 200px auto;
}
#dot {
width: 10px;
height: 10px;
background: red;
position: absolute;
border-radius: 5px;
left: 200px;
top: 0;
}
</style>
</head>
<body>
<div id="center">
<div id="dot"></div>
</div>
<script type="text/javascript">
var oDot = document.getElementById('dot');
var deg = 0;
var timer = null;
var radius = oDot.offsetLeft; // 旋转半径
timer = setInterval(function() {
var radian = (2*Math.PI/360)*deg;
var theTop = Math.ceil(Math.sin(radian)*radius);
var theLeft = Math.ceil(Math.cos(radian)*radius);
oDot.style.top = theTop + 'px';
oDot.style.left = theLeft + 'px';
deg += 0.5;
if (deg === 361) {
deg = 0;
}
},1);
</script>
</body>
</html>
