# Filter

Filter document allows you to specify what records should be returned.

## How to use

A format of a filter document is shown below. You provide a field, which is a field saved inside a database, and a value or selector.

```javascript
{ <field>: <value>, <field2>: { <selector> }, ... }
```

An example is shown below. Here we have two fields which we know exists in database. This will filter all the records with a name John and age greater than 18.

```javascript
{ "name": "John", "age": { "$gt": 18 } }
```

To filter items inside an object, separate fields by a dot.

```javascript
{ "address.house_number": 202 }
```

## External references

As CodeMash is using MongoDB database internally, the following resources explain more on how to use filter.

* [Filter selectors](https://docs.mongodb.com/manual/reference/operator/query/#query-selectors)


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# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://docs.codemash.io/other-topics/list-parameters/filter.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.