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。

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

Amazon DocumentDB 中的`$indexOfCP`運算子用於尋找字串表達式中第一次出現指定子字串的索引，以程式碼點 (CP) 為單位。這在剖析和擷取字串欄位的內容時非常有用。

**參數**
+ `string expression`：要搜尋的字串。
+ `substring`：要搜尋的子字串。
+ `[<start>]`：（選用） 開始搜尋的位置 （以零為基礎的索引）。預設值為 0。

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

在此範例中，我們使用 `$indexOfCP`運算子在每個文件的桌面欄位中尋找第一個連字號字元的索引。

**建立範例文件**

```
db.people.insertMany([
  { "_id":1, "name":"John Doe", "Manager":"Jane Doe", "Role":"Developer", "Desk": "Düsseldorf-BVV-021"},
  { "_id":2, "name":"John Stiles", "Manager":"Jane Doe", "Role":"Manager", "Desk": "Munich-HGG-32a"},
  { "_id":3, "name":"Richard Roe", "Manager":"Jorge Souza", "Role":"Product", "Desk": "Cologne-ayu-892.50"},
  { "_id":4, "name":"Mary Major", "Manager":"Jane Doe", "Role":"Solution Architect", "Desk": "Dortmund-Hop-78"}
])
```

**查詢範例**

```
db.people.aggregate([
  { $project: { stateLocation: { $indexOfCP: [ "$Desk", "-"] } } }
])
```

**輸出**

```
{ "_id" : 1, "stateLocation" : 10 }
{ "_id" : 2, "stateLocation" : 6 }
{ "_id" : 3, "stateLocation" : 7 }
{ "_id" : 4, "stateLocation" : 8 }
```

## 程式碼範例
<a name="indexOfCP-code"></a>

若要檢視使用 `$indexOfCP`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 main() {
  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: { stateLocation: { $indexOfCP: [ "$Desk", "-"] } } }
  ]).toArray();

  console.log(result);

  await client.close();
}

main();
```

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

```
from pymongo import MongoClient

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([
    { '$project': { 'stateLocation': { '$indexOfCP': [ '$Desk', '-' ] } } }
]))

print(result)

client.close()
```

------