> Portal Navigation:
> 
> - Append `.md` to any URL under `https://dev.wix.com/docs/` to get its markdown version.
> - Pages are either content pages (article or reference text) or menu pages (a list of links to child pages).
> - To get a menu page, truncate any URL to a parent path and append `.md` (e.g. `https://dev.wix.com/docs/sdk.md`, `https://dev.wix.com/docs/sdk/core-modules.md`).
> - Top-level index of all portals: https://dev.wix.com/docs/llms.txt
> - Full concatenated docs: https://dev.wix.com/docs/llms-full.txt

## Resource: $w

## Namespace: wix-data-filter

## Article: Introduction

## Article Link: https://dev.wix.com/docs/velo/velo-only-apis/$w/wix-data-filter/introduction.md

## Article Content:

# Introduction
The `WixDataFilter` functions enable you to filter and control which results are returned by a dataset when the
[`setFilter()`](https://dev.wix.com/docs/velo/api-reference/$w/dataset/set-filter.md) function is applied.

A filter is used to control which data is contained in a dataset on your page.

Typically, you  build a filter using the [`filter()`](https://dev.wix.com/docs/velo/api-reference/wix-data/filter.md) function, refine the filter with `WixDataFilter` functions, and then apply the filter to the dataset using the [`setFilter()`](https://dev.wix.com/docs/velo/api-reference/$w/dataset/set-filter.md) function.

For example, the following code shows a filter on a dataset that's connected to a collection containing customer data. The filter includes only customers over the age of 20:

```javascript
const customerFilter = $w("#myDataset").filter().gt("age", 20);

$w("#myDataset").setFilter(customerFilter);
```
When working with [Wix app collections](https://support.wix.com/en/article/velo-working-with-wix-app-collections-and-code), check [which fields](https://support.wix.com/en/search?term=velo%20collection%20fields) can be used in a filter.