先贴上核心代码parabola.js：
/*!
* by zhangxinxu(.com) 2012-12-27
* you can visit http://www.zhangxinxu.com/wordpress/?p=3855 to get more infomation
* under MIT license
*/
var funParabola = function(element, target, options) {
/*
* 网页模拟现实需要一个比例尺
* 如果按照1像素就是1米来算，显然不合适，因为页面动不动就几百像素
* 页面上，我们放两个物体，200~800像素之间，我们可以映射为现实世界的2米到8米，也就是100:1
* 不过，本方法没有对此有所体现，因此不必在意
*/
var defaults = {
speed: 166.67, // 每帧移动的像素大小，每帧（对于大部分显示屏）大约16~17毫秒
curvature: 0.001, // 实际指焦点到准线的距离，你可以抽象成曲率，这里模拟扔物体的抛物线，因此是开口向下的
progress: function() {},
complete: function() {}
};
var params = {}; options = options || {};
for (var key in defaults) {
params[key] = options[key] || defaults[key];
}
var exports = {
mark: function() { return this; },
position: function() { return this; },
move: function() { return this; },
init: function() { return this; }
};
/* 确定移动的方式
* IE6-IE8 是margin位移
* IE9+使用transform
*/
var moveStyle = "margin", testDiv = document.createElement("div");
if ("oninput" in testDiv) {
["", "ms", "webkit"].forEach(function(prefix) {
var transform = prefix + (prefix? "T": "t") + "ransform";
if (transform in testDiv.style) {
moveStyle = transform;
}
});
}
// 根据两点坐标以及曲率确定运动曲线函数（也就是确定a, b的值）
/* 公式： y = a*x*x + b*x + c;
*/
var a = params.curvature, b = 0, c = 0;
// 是否执行运动的标志量
var flagMove = true;
if (element && target && element.nodeType == 1 && target.nodeType == 1) {
var rectElement = {}, rectTarget = {};
// 移动元素的中心点位置，目标元素的中心点位置
var centerElement = {}, centerTarget = {};
// 目标元素的坐标位置
var coordElement = {}, coordTarget = {};
// 标注当前元素的坐标
exports.mark = function() {
if (flagMove == false) return this;
if (typeof coordElement.x == "undefined") this.position();
element.setAttribute("data-center", [coordElement.x, coordElement.y].join());
target.setAttribute("data-center", [coordTarget.x, coordTarget.y].join());
return this;
}
exports.position = function() {
if (flagMove == false) return this;
var scrollLeft = document.documentElement.scrollLeft || document.body.scrollLeft,
scrollTop = document.documentElement.scrollTop || document.body.scrollTop;
// 初始位置
if (moveStyle == "margin") {
element.style.marginLeft = element.style.marginTop = "0px";
} else {
element.style[moveStyle] = "translate(0, 0)";
}
// 四边缘的坐标
rectElement = element.getBoundingClientRect();
rectTarget = target.getBoundingClientRect();
// 移动元素的中心点坐标
centerElement = {
x: rectElement.left + (rectElement.right - rectElement.left) / 2 + scrollLeft,
y: rectElement.top + (rectElement.bottom - rectElement.top) / 2 + scrollTop
};
// 目标元素的中心点位置
centerTarget = {
x: rectTarget.left + (rectTarget.right - rectTarget.left) / 2 + scrollLeft,
y: rectTarget.top + (rectTarget.bottom - rectTarget.top) / 2 + scrollTop
};
// 转换成相对坐标位置
coordElement = {
x: 0,
y: 0
};
coordTarget = {
x: -1 * (centerElement.x - centerTarget.x),
y: -1 * (centerElement.y - centerTarget.y)
};
/*
* 因为经过(0, 0), 因此c = 0
* 于是：
* y = a * x*x + b*x;
* y1 = a * x1*x1 + b*x1;
* y2 = a * x2*x2 + b*x2;
* 利用第二个坐标：
* b = (y2+ a*x2*x2) / x2
*/
// 于是
b = (coordTarget.y - a * coordTarget.x * coordTarget.x) / coordTarget.x;
return this;
};
// 按照这个曲线运动
exports.move = function() {
// 如果曲线运动还没有结束，不再执行新的运动
if (flagMove == false) return this;
var startx = 0, rate = coordTarget.x > 0? 1: -1;
var step = function() {
// 切线 y'=2ax+b
var tangent = 2 * a * startx + b;
// 下面是根据确定的移动速度，得到当前切线下x也就是水平方向移动的大小
// 已知两点之间的距离为
// Math.sqrt((x2-x1) * (x2-x1) + (y2-y1) * (y2-y1));
// 因此应当是
// Math.sqrt(△x*△x + △y*△y) = speed
// 因为写这段代码的时候，脑子不在线，所以，根号忘记了
// 就套用了下面的公式（导致很多小伙伴不理解，这里说声抱歉）
// 不过对于大功能并不影响，就是这个speed参数值有些大，哈哈
// y*y + x*x = speed
// (tangent * x)^2 + x*x = speed
// x = Math.sqr(speed / (tangent * tangent + 1));
startx = startx + rate * Math.sqrt(params.speed / (tangent * tangent + 1));
// 防止过界
if ((rate == 1 && startx > coordTarget.x) || (rate == -1 && startx < coordTarget.x)) {
startx = coordTarget.x;
}
var x = startx, y = a * x * x + b * x;
// 标记当前位置，这里有测试使用的嫌疑，实际使用可以将这一行注释
element.setAttribute("data-center", [Math.round(x), Math.round(y)].join());
// x, y目前是坐标，需要转换成定位的像素值
if (moveStyle == "margin") {
element.style.marginLeft = x + "px";
element.style.marginTop = y + "px";
} else {
element.style[moveStyle] = "translate("+ [x + "px", y + "px"].join() +")";
}
if (startx !== coordTarget.x) {
params.progress(x, y);
window.requestAnimationFrame(step);
} else {
// 运动结束，回调执行
params.complete();
flagMove = true;
}
};
window.requestAnimationFrame(step);
flagMove = false;
return this;
};
// 初始化方法
exports.init = function() {
this.position().mark().move();
};
}
return exports;
};
/*! requestAnimationFrame.js
* by zhangxinxu 2013-09-30
*/
(function() {
var lastTime = 0;
var vendors = ['webkit', 'moz'];
for(var x = 0; x < vendors.length && !window.requestAnimationFrame; ++x) {
window.requestAnimationFrame = window[vendors[x] + 'RequestAnimationFrame'];
window.cancelAnimationFrame = window[vendors[x] + 'CancelAnimationFrame'] || // name has changed in Webkit
window[vendors[x] + 'CancelRequestAnimationFrame'];
}
if (!window.requestAnimationFrame) {
window.requestAnimationFrame = function(callback, element) {
var currTime = new Date().getTime();
var timeToCall = Math.max(0, 16.7 - (currTime - lastTime));
var id = window.setTimeout(function() {
callback(currTime + timeToCall);
}, timeToCall);
lastTime = currTime + timeToCall;
return id;
};
}
if (!window.cancelAnimationFrame) {
window.cancelAnimationFrame = function(id) {
clearTimeout(id);
};
}
}());懒得粘贴就直接下载张鑫旭的parabola.js或者压缩版parabola-min.js.
可以后续工程拿来用，如果之前已有requestAnimationFrame动画兼容处理，代码下面部分可删除。或下载requestAnimationFrame.js
购物车功能DEMO：
<!DOCTYPE html>
<html lang="zh-cn">
<head>
<meta charset="UTF-8">
<title>抛物线动画-加入购物车</title>
<script type="text/javascript" src="parabola.js"></script>
<style>
body { overflow-x: hidden; }
img { vertical-align: bottom; }
.width_limit { width: 1194px; margin-left: auto; margin-right: auto; }
.image_limit { position: relative; }
.shop_cart { width: 283px; height: 25px; line-height: 25px; padding-top: 8px; background: orange; font-family: 'microsoft yahei'; font-size: 12px; text-indent: 34px; color: #000; position: fixed; right: 10px; bottom: 0; }
.add_cart_large, .add_cart_small { position: absolute; background: red; overflow: hidden;text-align: center;color: #FFF; }
.add_cart_large { width: 167px; height: 33px; left: 400px; top: 511px; }
.add_cart_small { width: 82px; height: 25px; left: 1098px; top: 1014px; }
.fly_item { border: 2px solid #B30000;background: blue; width: 50px; height: 50px; overflow: hidden; position: absolute; visibility: hidden; opacity: .5; filter: alpha(opacity=50); }
</style>
</head>
<body>
<div class="width_limit">
<p>下面这个是截图，只有两个“加入购物车”按钮可以点击：</p>
<div class="image_limit">
<a href="javascript:" class="add_cart_large btnCart" title="加入购物车">加入购物车</a>
<a href="javascript:" class="add_cart_small btnCart" title="加入购物车">加入购物车</a>
</div>
</div>
<div id="shopCart" class="shop_cart">购物车 <span>0</span></div>
<div id="flyItem" class="fly_item"></div>
<script type="text/javascript">
// 元素以及其他一些变量
var eleFlyElement = document.querySelector("#flyItem"), eleShopCart = document.querySelector("#shopCart");
var numberItem = 0;
// 抛物线运动
var myParabola = funParabola(eleFlyElement, eleShopCart, {
speed: 700,
curvature: 0.002,
complete: function() {
eleFlyElement.style.visibility = "hidden";
eleShopCart.querySelector("span").innerHTML = ++numberItem;
}
});
// 绑定点击事件
if (eleFlyElement && eleShopCart) {
[].slice.call(document.getElementsByClassName("btnCart")).forEach(function(button) {
button.addEventListener("click", function() {
// 滚动大小
var scrollLeft = document.documentElement.scrollLeft || document.body.scrollLeft || 0,
scrollTop = document.documentElement.scrollTop || document.body.scrollTop || 0;
eleFlyElement.style.left = event.clientX + scrollLeft + "px";
eleFlyElement.style.top = event.clientY + scrollTop + "px";
eleFlyElement.style.visibility = "visible";
// 需要重定位
myParabola.position().move();
});
});
}
</script>
</body>
</html>以上是实际使用加入购物车的功能的示例，以下是全代码示例，以备借鉴学习用：
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<meta http-equiv="description" content="javascript实现元素抛物线运动 » 张鑫旭-鑫空间-鑫生活" />
<meta name="description" content="张鑫旭web前端学习实例页面之javascript实现元素抛物线运动" />
<meta name="keywords" content="javascript, 动画, 抛物线" />
<meta name="author" content="张鑫旭, zhangxinxu" />
<title>抛物线运动</title>
<style>
body { margin: 0; font-size: 14px; font-family: 'microsoft yahei'; position: absolute; top: 0; right: 0; bottom: 0; left: 0; -webkit-user-select: none; -moz-user-select: none; user-select: none; }
p { margin: 1em; }
.target, .element { position: absolute; border: 1px solid #34538b; border-radius: 20px; }
.target { width: 100px; height: 40px; background-color: #f0f3f9; left: 480px; top: 300px; cursor: move; }
.target:active { box-shadow: inset 1px 1px 2px rgba(0,0,0,.35); }
.element { width: 30px; height: 30px; background-color: #34538b; left: 960px; top: 500px; font-size: 12px; pointer-events: none; }
.element:before { content: attr(data-center); color: #666; position: absolute; left: 100%; top: -10px; }
.target:before { content: attr(data-center); width: 100%; line-height: 40px; color: #666; position: absolute; text-align: center; }
.x { position: absolute; left: 0; top: 516px; right: 0; border-top: 1px solid #000; }
.x:before, .y:before { font-size: 40px; font-style: italic; font-family: Arial, Helvetica, sans-serif; position: absolute; }
.x:before { content: 'x'; top: 0; right: 5px; }
.y { position: absolute; left: 976px; top: 0; bottom: 0; border-left: 1px solid #000; }
.y:before { content: 'y'; left: 5px; top: 0; }
.article { display: inline-block; margin-left: 1em; color: #34538b; }
</style>
</head>
<body>
<p>点击屏幕任意区域开始运动，拖动椭圆目标至任意位置也能运动</p>
<div id="target" class="target"></div>
<div id="element" class="element"></div>
<i class="x" title="x轴"></i>
<i class="y" title="y轴"></i>
<a href="//www.zhangxinxu.com/wordpress/?p=3855" class="article">本demo相关文章»</a>
<script>
var funParabola = function(element, target, options) {
/*
* 网页模拟现实需要一个比例尺
* 如果按照1像素就是1米来算，显然不合适，因为页面动不动就几百像素
* 页面上，我们放两个物体，200~800像素之间，我们可以映射为现实世界的2米到8米，也就是100:1
* 不过，本方法没有对此有所体现，因此不必在意
*/
var defaults = {
speed: 166.67, // 每帧移动的像素大小，每帧（对于大部分显示屏）大约16~17毫秒
curvature: 0.001, // 实际指焦点到准线的距离，你可以抽象成曲率，这里模拟扔物体的抛物线，因此是开口向下的
progress: function() {},
complete: function() {}
};
var params = {}; options = options || {};
for (var key in defaults) {
params[key] = options[key] || defaults[key];
}
var exports = {
mark: function() { return this; },
position: function() { return this; },
move: function() { return this; },
init: function() { return this; }
};
/* 确定移动的方式
* IE6-IE8 是margin位移
* IE9+使用transform
*/
var moveStyle = "margin", testDiv = document.createElement("div");
if ("oninput" in testDiv) {
["", "ms", "webkit"].forEach(function(prefix) {
var transform = prefix + (prefix? "T": "t") + "ransform";
if (transform in testDiv.style) {
moveStyle = transform;
}
});
}
// 根据两点坐标以及曲率确定运动曲线函数（也就是确定a, b的值）
/* 公式： y = a*x*x + b*x + c;
*/
var a = params.curvature, b = 0, c = 0;
// 是否执行运动的标志量
var flagMove = true;
if (element && target && element.nodeType == 1 && target.nodeType == 1) {
var rectElement = {}, rectTarget = {};
// 移动元素的中心点位置，目标元素的中心点位置
var centerElement = {}, centerTarget = {};
// 目标元素的坐标位置
var coordElement = {}, coordTarget = {};
// 标注当前元素的坐标
exports.mark = function() {
if (flagMove == false) return this;
if (typeof coordElement.x == "undefined") this.position();
element.setAttribute("data-center", [coordElement.x, coordElement.y].join());
target.setAttribute("data-center", [coordTarget.x, coordTarget.y].join());
return this;
}
exports.position = function() {
if (flagMove == false) return this;
var scrollLeft = document.documentElement.scrollLeft || document.body.scrollLeft,
scrollTop = document.documentElement.scrollTop || document.body.scrollTop;
// 初始位置
if (moveStyle == "margin") {
element.style.marginLeft = element.style.marginTop = "0px";
} else {
element.style[moveStyle] = "translate(0, 0)";
}
// 四边缘的坐标
rectElement = element.getBoundingClientRect();
rectTarget = target.getBoundingClientRect();
// 移动元素的中心点坐标
centerElement = {
x: rectElement.left + (rectElement.right - rectElement.left) / 2 + scrollLeft,
y: rectElement.top + (rectElement.bottom - rectElement.top) / 2 + scrollTop
};
// 目标元素的中心点位置
centerTarget = {
x: rectTarget.left + (rectTarget.right - rectTarget.left) / 2 + scrollLeft,
y: rectTarget.top + (rectTarget.bottom - rectTarget.top) / 2 + scrollTop
};
// 转换成相对坐标位置
coordElement = {
x: 0,
y: 0
};
coordTarget = {
x: -1 * (centerElement.x - centerTarget.x),
y: -1 * (centerElement.y - centerTarget.y)
};
/*
* 因为经过(0, 0), 因此c = 0
* 于是：
* y = a * x*x + b*x;
* y1 = a * x1*x1 + b*x1;
* y2 = a * x2*x2 + b*x2;
* 利用第二个坐标：
* b = (y2+ a*x2*x2) / x2
*/
// 于是
b = (coordTarget.y - a * coordTarget.x * coordTarget.x) / coordTarget.x;
return this;
};
// 按照这个曲线运动
exports.move = function() {
// 如果曲线运动还没有结束，不再执行新的运动
if (flagMove == false) return this;
var startx = 0, rate = coordTarget.x > 0? 1: -1;
var step = function() {
// 切线 y'=2ax+b
var tangent = 2 * a * startx + b; // = y / x
// y*y + x*x = speed
// (tangent * x)^2 + x*x = speed
// x = Math.sqr(speed / (tangent * tangent + 1));
startx = startx + rate * Math.sqrt(params.speed / (tangent * tangent + 1));
// 防止过界
if ((rate == 1 && startx > coordTarget.x) || (rate == -1 && startx < coordTarget.x)) {
startx = coordTarget.x;
}
var x = startx, y = a * x * x + b * x;
// 标记当前位置，这里有测试使用的嫌疑，实际使用可以将这一行注释
element.setAttribute("data-center", [Math.round(x), Math.round(y)].join());
// x, y目前是坐标，需要转换成定位的像素值
if (moveStyle == "margin") {
element.style.marginLeft = x + "px";
element.style.marginTop = y + "px";
} else {
element.style[moveStyle] = "translate("+ [x + "px", y + "px"].join() +")";
}
if (startx !== coordTarget.x) {
params.progress(x, y);
window.requestAnimationFrame(step);
} else {
// 运动结束，回调执行
params.complete();
flagMove = true;
}
};
window.requestAnimationFrame(step);
flagMove = false;
return this;
};
// 初始化方法
exports.init = function() {
this.position().mark().move();
};
}
return exports;
};
// 这是很简单的拖拽方法，与本demo主旨无关，方便演示使用
var funDrag = function(element, callback) {
callback = callback || function() {};
var params = {
left: 0,
top: 0,
currentX: 0,
currentY: 0,
flag: false
};
//获取相关CSS属性
var getCss = function(o,key){
return o.currentStyle? o.currentStyle[key] : document.defaultView.getComputedStyle(o,false)[key];
};
//拖拽的实现
if(getCss(element, "left") !== "auto"){
params.left = getCss(element, "left");
}
if(getCss(element, "top") !== "auto"){
params.top = getCss(element, "top");
}
//o是移动对象
element.onmousedown = function(event){
params.flag = true;
event = event || window.event;
params.currentX = event.clientX;
params.currentY = event.clientY;
};
document.onmouseup = function(){
params.flag = false;
if(getCss(element, "left") !== "auto"){
params.left = getCss(element, "left");
}
if(getCss(element, "top") !== "auto"){
params.top = getCss(element, "top");
}
callback();
};
document.onmousemove = function(event){
event = event || window.event;
if(params.flag){
var nowX = event.clientX, nowY = event.clientY;
var disX = nowX - params.currentX, disY = nowY - params.currentY;
element.style.left = parseInt(params.left) + disX + "px";
element.style.top = parseInt(params.top) + disY + "px";
}
}
};
/* 元素 */
var element = document.getElementById("element"), target = document.getElementById("target");
// 抛物线元素的的位置标记
var parabola = funParabola(element, target).mark();
// 拖拽
funDrag(target);
// 抛物线运动的触发
document.body.onclick = function() {
element.style.marginLeft = "0px";
element.style.marginTop = "0px";
parabola.init();
};
</script>
</body>
</html>
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