奇怪的代码运行

large='';
$.post("/sugarplus/Showg/getOne",{id:sign[0],type:sign[1],forward:sign[2]?sign[2]:""},function(result){
result1=eval("("+result+")");
if(1==result1.status){
large="/sugarplus"+result1.data.bigurl;
if(result1.data.attach!="null"){
//alert("aaa");
$("#h2pinglun").empty();
// $("#h2pinglun").append("sssssdf45454ss").show();
//alert(result1.data.attach[0]['reply'][0]['id']);
var key1;
var key2;
//循环输出评论
for(key1 in result1.data.attach){
var tempDom='';
tempDom+='<img src="/sugarplus'+result1.data.attach[key1]['uheader']+'" />'+
'<span>'+
'<p>'+
'<a href="#">'+result1.data.attach[key1]['uname']+'：</a>'+result1.data.attach[key1]['info']+
'<p class="time">'+
'<a href="#">'+result1.data.attach[key1]['time']+'</a><input type="button" value="回复" onclick="show(\'pid_2\')" />'+
'</p>'+
'<p class="one" id="pid_2" style="display:none;">'+
'<textarea style="width:300px;height:40px;margin-left:80px;"></textarea>'+
'<b><input type="button" value="发表" /></b>'+
'</p>'+
'<h4 id="huifu">';
if(result1.data.attach[key1]['reply']!="null"){
//如果有回复,循环添加回复到评论中；
for(var key2 in result1.data.attach[key1]['reply']){
tempDom+='<img src="/sugarplus'+result1.data.attach[key1]['reply'][key2]['uheade']+'" />'+
'<span>'+
'<p>'+
'<a href="#">'+result1.data.attach[key1]['reply'][key2]['uname']+':</a>'+
result1.data.attach[key1]['reply'][key2]['info']+
'</p>'+
'<p class="time">'+
'<a href="#">'+result1.data.attach[key1]['reply'][key2]['time']+'</a>'+
'</p>'+
'</span>'+
'</h4>'+
'</p>'+
'</span>';
}
}
$("#h2pinglun").append(tempDom).show();
}
}
}
//alert("aaa");
});
重点在这，下面主调的alert，一旦注掉程序运行就不正确，打开，就没问题，很是个神奇。
//alert("large");
if(typeof(large)=="undefined"){
return false;
}