javascript链式运动框架
任务描述：
当鼠标移入红色矩形时，该矩形宽度逐渐增加至400px，之后高度逐渐增加至400px;
当鼠标移出红色矩形时，该矩形高度逐渐减小至200px，之后宽度逐渐减小至200px。
效果图：
<!DOCTYPE html>
<html lang="zh-CN">
<head>
<meta charset="UTF-8">
<title>JS小案例：多物体变宽</title>
<style>
body {
height: 2000px;
margin: 0px;
}
div {
200px;
height: 200px;
background: red;
margin: 10px;
}
</style>
<script>
window.onload = function () {
//补充代码
}
</script>
</head>
<body>
<div id='div1'></div>
</body>
</html>
参考代码：
oDiv1 = document.getElementById('div1');
oDiv1.onmouseover = function () {
startMove(oDiv1, 'width', 400, function () {
startMove(oDiv1, 'height', 400)
});
}
oDiv1.onmouseout = function () {
startMove(oDiv1, 'height', 200, function () {
startMove(oDiv1, 'width', 200)
});
}
function getStyle(obj, name) {
if (obj.currentStyle) {
return obj.currentStyle[name];
}
else {
return getComputedStyle(obj, null)[name];
}
}
function startMove(obj, attr, iTarget, fnEnd) {
clearInterval(obj.timer);
obj.timer = setInterval(function () {
var cur = 0;
if (attr == 'opacity') {
//Math.round()四舍五入取整主要是针对低浮点数的精度问题。
cur = Math.round(parseFloat(getStyle(obj, attr)) * 100);
} else {
cur = parseInt(getStyle(obj, attr));
}
var speed = (iTarget - cur) / 6;
speed = speed > 0 ? Math.ceil(speed) : Math.floor(speed);
if (cur == iTarget) {
clearInterval(obj.timer);
if (fnEnd) {
fnEnd();
}
} else {
if (attr == 'opacity') {
obj.style.opacity = (cur + speed) / 100;
obj.style.filter = 'alpha(opacity=' + (cur + speed) + ")";
}
else {
obj.style[attr] = cur + speed + 'px';
}
}
}, 30)
}