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

4.0 版的新功能

Amazon DocumentDB 中的`$trim`運算子用於從字串中移除開頭和/或結尾空格字元。

**參數**
+ `input`：要修剪的字串表達式。
+ `chars`：（選用） 指定要從輸入開頭和結尾修剪的字元，預設值為空格。

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

下列範例示範如何使用 `$trim`運算子從字串中移除開頭和結尾空格。

**建立範例文件**

```
db.people.insertMany([
  { "name": "   John Doe   " },
  { "name": "   Bob Johnson   " }
])
```

**查詢範例**

```
db.people.aggregate([
  { $project: {
    "name": { $trim: {input: "$name"}}
  }}
])
```

**輸出**

```
[
  { "name": "John Doe" },
  { "name": "Bob Johnson" }
]
```

## 程式碼範例
<a name="trim-code"></a>

若要檢視使用 `$trim`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 example() {
  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('people');

  const result = await collection.aggregate([
    { $project: {
      "name": { $trim: {input: "$name" }}
    }}
  ]).toArray();

  console.log(result);
  client.close();
}

example();
```

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

```
from pymongo import MongoClient

def example():
    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['people']

    result = list(collection.aggregate([
        {"$project": {
            "name": {"$trim": {"input": "$name"}}
        }}
    ]))

    print(result)
    client.close()

example()
```

------