请大神帮我看看，为何 arraysSimilar([,'3',4],[,3,4]) 弹出为true，好像是for in循环哪里出错了，改成普通for循环就没问题，求大神解答
<!DOCTYPE HTML>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=gb18030">
<title>比较两个数组</title>
</head>
<body>
<script type="text/javascript">
/*
* param1 Array
* param2 Array
* return true or false
*/
function type(a){
return a === null ? '[object Null]':Object.prototype.toString.apply(a); //hack ie678
}
function arraysSimilar(arr1, arr2){
if(arr1 instanceof Array && arr2 instanceof Array && arr1.length==arr2.length){
var arr11=[],arr22=[];
for(var i in arr1){
arr11.push(arr1[i]);
arr22.push(arr2[i]);
}
var arrs1=arr11.sort(),arrs2=arr22.sort(),ty1=[],ty2=[];
for(var i in arr1){
//alert( Object.prototype.toString.apply(arr1[i]))
ty1.push(type(arrs1[i]));
ty2.push(type(arrs2[i]));
}
// alert(ty1+'\n'+ty2)
var str1=arrs1.toString();
var str2=arrs2.toString();
var str3=ty1.toString();
var str4=ty2.toString();
if(str1==str2&&str3==str4){
return true
}else{return false}
}else{return false}
}
alert(arraysSimilar([,'3',4],[,3,4]))
</script>
</body>
</html>
