for(type in{Top:"",Left:""})这句是什么意思，坐等大神讲解
(function(){function k(a,b,c){ if(a.addEventListener) a.addEventListener(b,c,false); else a.attachEvent&&a.attachEvent("on"+b,c)}function g(a){ if(typeof window.onload!="function") window.onload=a; else{ var b=window.onload; window.onload=function(){ b(); a() } } }function h(){ var a={}; for(type in{Top:"",Left:""}){ var b=type=="Top"?"Y":"X"; if(typeof window["page"+b+"Offset"]!="undefined")a[type.toLowerCase()]=window["page"+b+"Offset"]; else{ b=document.documentElement.clientHeight?document.documentElement:document.body; a[type.toLowerCase()]=b["scroll"+type] } } return a}function l(){ var a=document.body,b; if(window.innerHeight)b=window.innerHeight; else if(a.parentElement.clientHeight)b=a.parentElement.clientHeight; else if(a&&a.clientHeight)b=a.clientHeight; return b }function i(a){ this.parent=document.body; this.createEl(this.parent,a); this.size=Math.random()*5+5; this.el.style.width=Math.round(this.size)+"px"; this.el.style.height=Math.round(this.size)+"px"; this.maxLeft=document.body.offsetWidth-this.size; this.maxTop=document.body.offsetHeight- this.size; this.left=Math.random()*this.maxLeft; this.top=h().top+1; this.angle=1.4+0.2*Math.random(); this.minAngle=1.4; this.maxAngle=1.6; this.angleDelta=0.01*Math.random(); this.speed=2+Math.random() }var j=false;g(function(){ j=true });var f=true;window.createSnow=function(a,b){ if(j){ var c=[],m=setInterval(function(){ f&&b>c.length&&Math.random()<b*0.0025&&c.push(new i(a)); !f&&!c.length&&clearInterval(m); for(var e=h().top,n=l(),d=c.length-1;d>=0;d--)if(c[d])if(c[d].top<e||c[d].top+c[d].size+1>e+n){ c[d].remove(); c[d]=null; c.splice(d,1) }else{ c[d].move(); c[d].draw() } },40); k(window,"scroll",function(){ for(var e=c.length-1;e>=0;e--)c[e].draw() }) }else g(function(){ createSnow(a,b) })};window.removeSnow=function(){ f=false }; i.prototype={ createEl:function(a,b){ this.el=document.createElement("img"); this.el.setAttribute("src",b+"snow"+Math.floor(Math.random()*4)+".gif"); this.el.style.position="absolute"; this.el.style.display="block"; this.el.style.zIndex="99999"; this.parent.appendChild(this.el) }, move:function(){ if(this.angle< this.minAngle||this.angle>this.maxAngle)this.angleDelta=-this.angleDelta; this.angle+=this.angleDelta; this.left+=this.speed*Math.cos(this.angle*Math.PI); this.top-=this.speed*Math.sin(this.angle*Math.PI); if(this.left<0)this.left=this.maxLeft; else if(this.left>this.maxLeft)this.left=0 }, draw:function(){ this.el.style.top=Math.round(this.top)+"px"; this.el.style.left=Math.round(this.left)+"px" }, remove:function(){ this.parent.removeChild(this.el); this.parent=this.el=null } }})();
else{
b=document.documentElement.clientHeight?document.documentElement:document.body;
a[type.toLowerCase()]=b["scroll"+type]
}
}
return a
}
Top:"",Left:""这句是什么意思？
[解决办法]
就是json的格式
var obj = {a: 1, b: 1};
alert(obj.a) // 1
var obj = {a: '', b: 1};
alert(obj.a) // 空字符