如何显示两个数组的重叠？

Question

我有以下两个数组。

学生出勤数组

"student_attendance": [
        {
            "month": "March",
            "item": [
                {
                    "year": 2018,
                    "day": 5,
                    "status": "Absent"
                },
                {
                    "year": 2018,
                    "day": 6,
                    "status": "Present"
                }
            ]
        },
        {
            "month": "April",
            "item": [
                {
                    "year": 2018,
                    "day": 2,
                    "status": "Present"
                },
                {
                    "year": 2018,
                    "day": 3,
                    "status": "Leave"
                }
            ]
        },
        {
            "month": "May",
            "item": [
                {
                    "year": 2018,
                    "day": 1,
                    "status": "Absent"
                },
                {
                    "year": 2018,
                    "day": 2,
                    "status": "Present"
                }
            ]
        }
    ]

Days Array

  day_arr : [
{month: "March",
item: [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30,31]},
{month: "April",
item: [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30]},
{month: "May",
item: [1,2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,20,21,22,23,24,25,26,27,28,29,30, 31]},
]

这是我的尝试

<ng-container *ngFor="let d of day_arr;">
                        <ng-container *ngFor="let i of att.item;">
                          <ng-container *ngIf="att.month == d.month">
                            <ng-container *ngFor="let di of d.item;">
                                <td *ngIf="att.month == d.month && di == i.day;else not">
                                  {{ i.status }}
                                </td>
                                <ng-template #not>
                                  <td>{{ "-" }}</td>
                                </ng-template>
                            </ng-container>    
                          </ng-container>  
                        </ng-container>
                      </ng-container>

我遇到了如何用两个循环绑定数据的问题？我想拍照2风格，但我得到pic1风格。然后我不知道如何打破* ngFor？任何帮助将不胜感激。谢谢。

图片1

PIC2