前者循环的是属性，后者循环的才是数组。 若项目中对数组属性进行了扩展，那切记不能使用前者，否则在循环数组时扩展的函数体也会被当做数据返回。 var data = { p1:1, p2:"b" }; for (var i in data){ alert(eval（"data." + i)); } for(var i in items) 慎用 尤其在需要兼容IE8时。

for(var i in items) 和 for(var i;i<items.length;i++) 区别_sql

 

eg:

for(var i in items) 和 for(var i;i<items.length;i++) 区别_数组_02

for(var i in items) 和 for(var i;i<items.length;i++) 区别_数组_03

var data=
[
    {
        "LAY_TABLE_INDEX": 0,
        "createTime": "2019-11-20 17:13:11",
        "createUser": "8",
        "id": 92,
        "mergeFlag": 0,
        "onlineFlag": 0,
        "querySql": "select u.user_login_name as userLoginName,u.user_name as userName,u.user_status as userStatus,r.role_name as roleName,u.creator,u.create_time as createTime,u.modifier,u.update_time as updateTime from system_user u left join system_user_role ur on ur.user_id=u.user_id left join system_role r on ur.role_id=r.role_id",
        "reportName": "用户统计报表",
        "reportType": "",
        "tableHeaderLevel": 3
    },
    {
        "LAY_TABLE_INDEX": 1,
        "createTime": "2019-11-20 17:13:11",
        "createUser": "8",
        "id": 93,
        "mergeFlag": 1,
        "querySql": "select section_owner_name as owner,section_name as roadsubsection,toll_station_name as tollstation,lanetype as lanetype,cardtype as cardtype,type as inletandoutlet,bus1 as passenger1,bus2 as passenger2,bus3 as passenger3,bus4 as passenger4,bus_traffic as subtotal1,truck1,truck2,truck3,truck4,truck5,truck_traffic as subtotal2,traffic as total from st_etc_day_all_sum_dm_20191028",
        "reportBore": "fdsafd",
        "reportName": "ETC使用率报表修改",
        "reportType": "",
        "tableHeaderLevel": 4
    },
    {
        "LAY_TABLE_INDEX": 2,
        "createTime": "2019-12-05 14:51:09",
        "createUser": "8",
        "id": 104,
        "mergeFlag": 0,
        "onlineFlag": 0,
        "querySql": ",select section_owner_name ,section_name as roadsubsection,toll_station_name as tollstation,bus1 as passenger1,bus2 as passenger2,bus3 as passenger3,bus4 as passenger4,bus_traffic as subtotal1,traffic as total from st_etc_day_all_sum_dm_20191028",
        "reportBore": "fdgfds",
        "reportName": "ETC使用率报表96",
        "reportType": "1",
        "tableHeaderLevel": 3
    },
    {
        "LAY_TABLE_INDEX": 3,
        "createTime": "2019-12-05 14:59:14",
        "createUser": "8",
        "id": 106,
        "mergeFlag": 0,
        "onlineFlag": 0,
        "querySql": "select section_owner_name ,section_name as roadsubsection,toll_station_name as tollstation,bus1 as passenger1,bus2 as passenger2,bus3 as passenger3,bus4 as passenger4,bus_traffic as subtotal1,traffic as total from st_etc_day_all_sum_dm_20191028",
        "reportBore": "dsddfdf",
        "reportName": "ETC使用率报表修改",
        "reportType": "1",
        "tableHeaderLevel": 3
    },
    {
        "LAY_TABLE_INDEX": 4,
        "accountPerType": 1,
        "createTime": "2019-12-19 10:04:27",
        "createUser": "8",
        "id": 107,
        "mergeFlag": 1,
        "onlineFlag": 0,
        "querySql": "select id,type,mjnumber,source,sum,secussssum,secusslv,descf from hsop_test order by id",
        "reportBore": "测试合并",
        "reportName": "测试合并",
        "reportType": "1",
        "tableHeaderLevel": 2
    },
    {
        "LAY_TABLE_INDEX": 5,
        "accountPerType": 1,
        "createTime": "2019-12-19 10:56:44",
        "createUser": "8",
        "id": 108,
        "mergeFlag": 1,
        "onlineFlag": 0,
        "querySql": "select id,type,mjnumber,source,sum,secussssum,secusslv,descf from hsop_test order by id",
        "reportBore": "dddd",
        "reportName": "wenjinhong",
        "reportType": "1",
        "tableHeaderLevel": 2
    }
]


for (var item in data) {
            console.log(data[item]);
            console.log(data[item].id);

}

View Code

结果：

for(var i in items) 和 for(var i;i<items.length;i++) 区别_数组_04