访问嵌套的json时获取未定义

Question

我希望从以下JSON数据中检索people_id，username，name和people_type。最后，我必须在bootstrap模式表中填充这些细节。下列 是我用来检索细节的jQuery代码：

.done(function (data_, textStatus_, jqXHR_) {
 $.each(data_.people_list, function(key, value) {

                    $.each(value.details_list, function(k,v) { 
                              console.log("Inside Loop:"+v.name); 
                              $.each(v.role, function(k1,v1) { 
                              console.log("Inside Another Loop for Role Name:"+v1.people_type); 
                              }); 
                    });
              });  

 })

目前我只尝试访问name和people_type。这是我在控制台上获得的输出：

 Inside Loop:First Hand Details
 Inside Another Loop for Role Name:undefined
 Inside Loop:First Hand Details
 Inside Another Loop for Role Name:undefined
 Inside Loop:UAB Multiple Myeloma Registry
 Inside Another Loop for Role Name:undefined
 Inside Loop:First Hand Details
 Inside Another Loop for Role Name:undefined
 Inside Loop:First Hand Details
 Inside Another Loop for Role Name:undefined
 Inside Loop:First Hand Details
 Inside Another Loop for Role Name:undefined

为什么people_type未定义？我在网上看到当某个特定的东西不存在时，会得到undefined吗？

{
  "webservice_status" : {
    "status" : "SUCCESS",
    "message" : ""
  },
  "people_list" : [ {
    "people_id" : 001,
    "username" : "pxy123",
    "full_name" : "James Camerion",
    "details_list" : [ {
      "id" : 1234,
      "name" : "First Hand Details",
      "role" : {
        "type_id" : 3042,
        "people_type" : "SuperUser"
      }
    } ]
  }, {
    "people_id" : 002,
    "username" : "gbt123",
    "full_name" : "Tom Cruise",
    "details_list" : [ {
      "id" : 1234,
      "name" : "First Hand Details",
      "role" : {
        "type_id" : 3041,
        "people_type" : "Normal User"
      }
    }, {
      "id" : 5678,
      "name" : "Second Hand Details",
      "role" : {
        "type_id" : 3042,
        "people_type" : "SuperUser"
      }
    } ]
  }, {
    "people_id" : 003,
    "username" : "txt456",
    "full_name" : "Michael Jordon",
    "details_list" : [ {
      "id" : 1234,                                                                                                      
      "name" : "First Hand Details",
      "role" : {
        "type_id" : 3042,
        "people_type" : "SuperUser"
      }
    } ]
  }, {
    "people_id" : 004,
    "username" : "mxn788",
    "full_name" : "Paul Walker",
    "details_list" : [ {
      "id" : 1234,
      "name" : "First Hand Details",
      "role" : {
        "type_id" : 3042,
        "people_type" : "SuperUser"
      }
    } ]
  }, {
    "people_id" : 005,
    "username" : "nhgy234",
    "full_name" : "Brad Pitt",
    "details_list" : [ {
      "id" : 1234,
      "name" : "First Hand Details",
      "role" : {
        "type_id" : 3042,
        "people_type" : "SuperUser"
      }
    } ]
  } ]
}