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

Amazon DocumentDB 中的`$indexOfCP`运算符用于以码点 (CP) 形式查找字符串表达式中指定子字符串首次出现的索引。这在解析和提取字符串字段中的内容时非常有用。

**参数**
+ `string expression`: 要搜索的字符串。
+ `substring`: 要搜索的子字符串。
+ `[<start>]`:（可选）开始搜索的位置（从零开始的索引）。默认值为 0。

## 示例（MongoDB 外壳）
<a name="indexOfCP-examples"></a>

在此示例中，我们使用`$indexOfCP`运算符在每个文档的 Desk 字段中查找首次出现的连字符的索引。

**创建示例文档**

```
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"}
])
```

**查询示例**

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

**输出**

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

## 代码示例
<a name="indexOfCP-code"></a>

要查看使用该`$indexOfCP`命令的代码示例，请选择要使用的语言的选项卡：

------
#### [ 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()
```

------