fade方法
function fadeOut(steps){ doFade.call(this,steps/10,1,false); }; function fadeIn(steps){ doFade.call(this,steps/10,0,true); }; function doFade(steps,value,action,fn){ var ie=undefined!==window.ActiveXObject,calls=arguments.callee,t=this,step;value+=(action?1:-1)/steps,(action?value>1: value<0) && (value=action?1:0),ie===true ? t.style.filter='alpha(opacity='+value*100+')' : t.style.opacity=value;(action?value<1:value>0) && setTimeout(function(){calls.call(t,steps,value,action,fn);},1000/steps);(action?value===1:value===0 && 'undefined'!==typeof fn) && ('function'===typeof fn && fn.call(t)); }