一个简单的js动画效果代码

var $m = $M("divAnimate");

_("btnAnimate").onclick = function(){
this.disabled = true;
var that = this;
$m.animate({left:"300px",top:"100px",width:"300px", height:"200px",opacity:0.3},{duration:5000,easing:Tween.Back.easeInOut}).delay(200)
.animate({left:"50px",top:"300px",width:"150px",height:"100px",opacity:0.8},{duration:2000,easing:Tween.Elastic.easeInOut,
callback:function(){
that.disabled = false;
}
});
}
_("btnPause").onclick = function(){
$m.pause();
this.disabled = true;
_("btnResume").disabled = false;
}
_("btnResume").disabled = true;
_("btnResume").onclick = function(){
$m.resume();
this.disabled = true;
_("btnPause").disabled = false;
}

_("btnStop").onclick = function(){
$m.stop();
_("btnAnimate").disabled = false;
}

/* 简单动画方法
* 未实现单位换算
*/
var $M = function(obj){
var elem = ("string" === typeof obj )?document.getElementById(obj):obj;
var _this = {},props = {},timeId,isBusy = false,isPause = false;
var queue = [],_current;
//直线运动算法
function Linear(t,b,c,d){ return c*t/d + b;}
function setCss(className,value){
if(className == "opacity"){
if(document.defaultView){
elem.style["opacity"] = value;
} else {
elem.style["filter"] = 'alpha(opacity=' + 100 * value + ')';
}
} else {
elem.style[className] = value;
}
}
function getCss(className){
if(className == "opacity"){
var ret = "";
if(document.defaultView){
ret = document.defaultView.getComputedStyle(elem,null)['opacity'] || 1;
} else {
ret = elem.currentStyle['filter']?(elem.currentStyle['filter'].match(/^alpha\(opacity=([\d\.]+)\)$/))[1]/100 : 1;
}
return ret.toString();
} else {
return elem.style[className].toString();
}
}

function _move(params,easing,st,ht,callback){
var t = ((new Date()).getTime() - st);
_current.t = t;
if(isPause){return;}
easing = easing||Linear;
ht = ht || 500;
for(var p in params){
if(!props[p]){
var iv = parseFloat(getCss(p)) || 0;
var ev = parseFloat(params[p]);
props[p] = {
iv:iv,
iu:iv?getCss(p).substring(iv.toString().length):null,
ev:ev,
eu:params[p].toString().substring(ev.toString().length)
}
//TODO(初始值的单位和目标值的单位不相同需要处理)
}
if(t >= ht){t = ht;}
var nv = easing(t,props[p].iv,(props[p].ev - props[p].iv),ht);
nv = parseFloat(nv);
setCss(p,nv + props[p].eu);
}

if(t < ht){
timeId = setTimeout(function(){
_move(params,easing,st,ht,callback);
},13);
} else {
props = {};
isBusy = false;
if(callback){
callback();
}
run();
}
}
function run(){
if(!isBusy && queue.length != 0){
var o = queue.shift();
var _delay = 0;
while(o && o.delay){
_delay += o.delay;
o = queue.shift();
}
if(o){
_current = o;
isBusy = true;
setTimeout(function(){
var st = (new Date()).getTime();
_move(o.params,o.options.easing,st,o.options.duration,o.options.callback);
},_delay);
}
}
}

var _this = {
animate:function(params,options){
queue.push({params:params,options:options});
isPause = false;
run();
return _this;
},
delay:function(ms){
queue.push({delay:ms});
return _this;
},
pause:function(){
isPause = true;
return _this;
},
resume:function(){
if(_current){
var o = _current;
isPause = false;
var st = (new Date()).getTime() - _current.t;
_move(o.params,o.options.easing,st,o.options.duration,o.options.callback);
return _this;
}
},
stop:function(){
isPause = true;
isBusy = false;
queue = [];
props = {};
return _this;
}
};
return _this;
}