1、有规律可循

A

packJson = [
{"name":"nikita", "password":"1111"},
{"name":"tony", "password":"2222"}
];
for(var p in packJson){//遍历json数组时，这么写p为索引，0,1
alert(packJson[p].name + " " + packJson[p].password);
}

B

for(var i = 0; i < packJson.length; i++){
alert(packJson[i].name + " " + packJson[i].password);
}

遍历json对象

myJson = {"name":"caibaojian", "password":"1111"};
for(var p in myJson){//遍历json对象的每个key/value对,p为key
alert(p + " " + myJson[p]);
}

无规律

var json = [
　　{dd:'SB',AA:'东东',re1:123},
　　{cccc:'dd',lk:'1qw'}
];
for(var i=0,l=json.length;i<l;i++){
　　for(var key in json[i]){
　　　　alert(key+':'+json[i][key]);
　　}
}