1. 遍历json对象的字段
var json = {"name":"bob", "password":"111"} ;
for(var k in json ){
  // 遍历每个key/value对, k为key
  alert(k + " " + json[k]);
}
// 等价于 
alert(json["name"]);
alert(json["password"]);
  1. 遍历json数组中的对象
var arr = [{"name":"bob", "password":"111"}, {"name":"mike", "password":"222"}];
for(var i in arr ){
  // 遍历json 数组时,i为索引
  alert(arr[i].name + " " + arr[i].password);
}