Javascript实现重力弹跳拖拽运动效果示例

演示地址：
http://www.ihuxu.com/project/gcdmove/

调用示例：
var GCDM = gcdMove(oDiv,100,0);
GCDM.startMove();//开始运动
GCDM.stopMove();//结束运动
该段JS代码已经封装好了，代码如下：
简要说明 - obj为要改动的对象元素，通常为某个div；iSpeedX，iSpeedY为div出师的横向（右侧），竖向（下）的初始速度，当然也可以设为零。
复制代码 代码如下:

function gcdMove(obj, iSpeedX, iSpeedY) {
_this = this;//public identifier
//construct fun
var gcdMove;
//self defined fun
var start;
_this.startMove;
//other var
var iTimer;
var iLastX = 0;
var iLastY = 0;
//construct fun
start = function() {
clearInterval(iTimer);
iTimer = setInterval(function() {
iSpeedY += 3;
var l = obj.offsetLeft + iSpeedX;
var t = obj.offsetTop + iSpeedY;
if (t >= document.documentElement.clientHeight - obj.offsetHeight) {
iSpeedY *= -0.8;
iSpeedX *= 0.8;
t = document.documentElement.clientHeight - obj.offsetHeight;
} else if (t <= 0) {
iSpeedY *= -1;
iSpeedX *= 0.8;
t = 0;
}
if (l >= document.documentElement.clientWidth - obj.offsetWidth) {
iSpeedX *= -0.8;
l = document.documentElement.clientWidth - obj.offsetWidth;
} else if (l <= 0) {
iSpeedX *= -0.8;
l = 0;
}
if (Math.abs(iSpeedX) < 1) {
iSpeedX = 0;
}
if (iSpeedX == 0 && iSpeedY == 0 && t == document.documentElement.clientHeight - obj.offsetHeight) {
clearInterval(iTimer);
}
obj.style.left = l + 'px';
obj.style.top = t + 'px';
}, 30);
}
_this.startMove = function(){
obj.onmousedown = function(ev) {
clearInterval(iTimer);
var oEvent = ev || event;
var disX = oEvent.clientX - obj.offsetLeft;
var disY = oEvent.clientY - obj.offsetTop;
document.onmousemove = function(ev) {
var oEvent = ev || event;
var l = oEvent.clientX - disX;
var t = oEvent.clientY - disY;
obj.style.left = l + 'px';
obj.style.top = t + 'px';
if(iLastX ==0){
iLastX = l;
}
if(iLastY == 0){
iLastY = t;
}
iSpeedX = l - iLastX;
iSpeedY = t - iLastY;
iLastX = l;
iLastY = t;
}
}
obj.onmouseup = function() {
document.onmousedown = null;
document.onmousemove = null;
document.onmouseup = null;
start();
}
start();
}
_this.stopMove = function(){
clearInterval(iTimer);
obj.onmousedown = null;
document.onmousemove = null;
obj.onmouseup = null;
iLastX = 0;
iLastY = 0;
iSpeedX = 0;
iSpeedY = 0;
disX = 0;
disY = 0;
}
//ConSTRUCT AREA
var gcdMove = function() {
if (!iSpeedX) {
iSpeedX = 0;
}
if (!iSpeedY) {
iSpeedY = 0;
}
}
gcdMove();
}