function startMove(obj,attr,iTarget,fn){
...
  if(iCur==iTarget){
    clearInterval(obj.timer);
    fn();
  }...
};

startMove(this,'width',300,function(){
  startMove(this,'height',300,function(){
    startMove(this,'opacity',100);
  });
});

startMove(this,'width',300);
startMove(this,'height',300);

function setStyle(obj,attr,value){
  obj.style[attr]=value;
};
setStyle(oDiv,'width','300px');
setStyle(oDiv,'height','300px');
setStyle(oDiv,'background','green');

function setStyle(obj,json){
  var attr='';
  for(attr in json){
    obj.style[attr]=json[attr];
  }
};
setStyle(oDiv,{width:'300px',height:'300px',background:'green'});

function startMove(obj,json,fn){
  clearInterval(obj.timer);
  obj.timer=setInterval(function(){
    for(var attr in json){
 　　  if(attr=='opacity'){
        var iCur=parseInt(parseFloat(getStyle(obj,attr))*100);
      }
      else{
        var iCur=parseInt(getStyle(obj,attr));
      }
      var iSpeed=(json[attr]-iCur)/8;
      iSpeed=iSpeed>0?Math.ceil(iSpeed):Math.floor(iSpeed);
      if(iCur==json[attr]){
        clearInterval(obj.timer);
        if(fn){
         fn();  //有传函数这个参数才执行，不然会出错
        }
      }
      else{
        if(attr=='opacity'){
          obj.style.filter='alpha(opacity:'+(iCur+iSpeed)+')';
          obj.style.opacity=(iCur+iSpeed)/100;
        }
        else{
          obj.style[attr]=iCur+iSpeed+'px'
        }
      }
    }
  },30);
};

if(iCur==json[attr]){
  clearInterval(obj.timer);
}

function startMove(obj,json,fn){
  clearInterval(obj.timer);
  obj.timer=setInterval(function(){
    var bStop=true;  //先定义一个值，假设所有值都到了
    for(var attr in json){
 　　  if(attr=='opacity'){
        var iCur=parseInt(parseFloat(getStyle(obj,attr))*100);
      }
      else{
        var iCur=parseInt(getStyle(obj,attr));
      }
      var iSpeed=(json[attr]-iCur)/8;
      iSpeed=iSpeed>0?Math.ceil(iSpeed):Math.floor(iSpeed);
      if(iCur!=json[attr]){
        bStop=false;    //并不是所有值都到了，就把bStop设成 false
      }
      if(attr=='opacity'){
        obj.style.filter='alpha(opacity:'+(iCur+iSpeed)+')';
        obj.style.opacity=(iCur+iSpeed)/100;
      }
      else{
        obj.style[attr]=iCur+iSpeed+'px'
      }
    }
    if(bStop){    //所有值都到了，关闭定时器
      clearInterval(obj.timer);
      if(fn){
        fn();  //有传函数这个参数才执行，不然会出错
      }
    }
  },30);
};