本文為英文版的機器翻譯版本，如內容有任何歧義或不一致之處，概以英文版為準。

# \$1position
<a name="position"></a>

Amazon DocumentDB `$position` 中的修飾詞會指定`$push`運算子插入元素的陣列中的位置。`$position` 如果沒有修改器，`$push`運算子會將元素插入陣列的結尾。

**參數**
+ `field`：要更新的陣列欄位。
+ `num`：陣列中應插入元素的位置，以零為基礎編製索引。

**注意**：若要使用`$position`修飾詞，它必須與`$each`修飾詞一起顯示。

## 範例 (MongoDB Shell)
<a name="position-examples"></a>

下列範例示範如何使用 `$position`運算子在專案管理系統中的特定位置插入任務。

**建立範例文件**

```
db.projects.insertOne({ "_id": 1, "name": "Website Redesign", "tasks": ["Design mockups"] })
```

**查詢範例 1 - 在開頭新增緊急任務**

```
db.projects.updateOne(
   { _id: 1 },
   {
     $push: {
        tasks: {
           $each: ["Security audit", "Performance review"],
           $position: 0
        }
     }
   }
)
```

**輸出 1**

```
{ "_id": 1, "name": "Website Redesign", "tasks": ["Security audit", "Performance review", "Design mockups"] }
```

**查詢範例 2 - 在特定位置新增任務**

```
db.projects.insertOne({ "_id": 2, "name": "Mobile App", "tasks": ["Setup project", "Create wireframes", "Deploy to store"] })

db.projects.updateOne(
   { _id: 2 },
   {
     $push: {
        tasks: {
           $each: ["Code review", "Testing phase"],
           $position: 2
        }
     }
   }
)
```

**輸出 2**

```
{ "_id": 2, "name": "Mobile App", "tasks": ["Setup project", "Create wireframes", "Code review", "Testing phase", "Deploy to store"] }
```

## 程式碼範例
<a name="position-code"></a>

若要檢視使用 `$position`命令的程式碼範例，請選擇您要使用的語言標籤：

------
#### [ Node.js ]

```
const { MongoClient } = require('mongodb');

async function insertTasksAtPosition() {
  const client = await MongoClient.connect('mongodb://<username>:<password>@<cluster-endpoint>:27017/?tls=true&tlsCAFile=global-bundle.pem&replicaSet=rs0&readPreference=secondaryPreferred&retryWrites=false');
  const db = client.db('test');
  const collection = db.collection('projects');

  await collection.updateOne(
    { _id: 1 },
    {
      $push: {
        tasks: {
          $each: ["Security audit", "Performance review"],
          $position: 0
        }
      }
    }
  );

  const updatedProject = await collection.findOne({ _id: 1 });
  console.log(updatedProject);

  await client.close();
}

insertTasksAtPosition();
```

------
#### [ Python ]

```
from pymongo import MongoClient

def insert_tasks_at_position():
    client = MongoClient('mongodb://<username>:<password>@<cluster-endpoint>:27017/?tls=true&tlsCAFile=global-bundle.pem&replicaSet=rs0&readPreference=secondaryPreferred&retryWrites=false')
    db = client['test']
    collection = db['projects']

    result = collection.update_one(
        {'_id': 1},
        {
            '$push': {
                'tasks': {
                    '$each': ['Security audit', 'Performance review'],
                    '$position': 0
                }
            }
        }
    )

    updated_project = collection.find_one({'_id': 1})
    print(updated_project)

    client.close()

insert_tasks_at_position()
```

------