# @maptalks/feature-filter

> Creates filtering function for features

Latest version **1.3.0** (published 2022-12-20) · 0 weekly downloads

## Install

```sh
npm install @maptalks/feature-filter
pnpm add @maptalks/feature-filter
yarn add @maptalks/feature-filter
bun add @maptalks/feature-filter
```

## Health

**Score 20/100 (F)** — status: abandoned.

Positive: esm support; no vulnerabilities.

Warnings: low downloads; no types.

Negative: abandoned; low maintenance score.

## Facts

| | |
|---|---|
| Version | 1.3.0 |
| Published | 2022-12-20 |
| First published | 2018-07-08 |
| Weekly downloads | 0 |
| TypeScript types | none |
| Module format | ESM + CommonJS |
| Dependencies | 0 |
| Unpacked size | 89.9 KB |
| Known vulnerabilities | 0 |
| Install scripts | no |
| GitHub stars | 2 |
| Maintainers | fuzhenn |

## Links

- npm: https://www.npmjs.com/package/@maptalks/feature-filter
- Repository: https://github.com/maptalks/feature-filter
- Homepage: https://github.com/maptalks/feature-filter#readme
- Issues: https://github.com/maptalks/feature-filter/issues
- npm.io page: https://npm.io/package/@maptalks/feature-filter

## Recent versions

- 1.3.0 (latest) — 2022-12-20
- 1.2.0 — 2022-09-21
- 1.1.0 — 2022-09-15
- 1.0.0 — 2018-07-08

## README

## Filter

[![CircleCI](https://circleci.com/gh/maptalks/feature-filter.svg?style=svg)](https://circleci.com/gh/maptalks/feature-filter)

Filter expressions are used to target specific data in a layer. This library implements the semantics specified by the [Mapbox GL JS spec](https://www.mapbox.com/mapbox-gl-style-spec/#filter).

### API

`featureFilter(filter)`

Given a filter expressed as nested arrays, return a new function
that evaluates whether a given feature (with a .properties or .tags property)
passes its test.

#### Parameters

| parameter | type  | description      |
| --------- | ----- | ---------------- |
| `filter`  | Array | mapbox gl filter |

**Returns** `Function`, filter-evaluating function

### Usage

``` javascript
var ff = require('feature-filter');

// will match a feature with class of street_limited,
// AND an admin_level less than or equal to 3,
// that's NOT a polygon.
var filter = [
    "all",
    ["==", "class", "street_limited"],
    ["<=", "admin_level", 3],
    ["!=", "$type", "Polygon"]
]

// will match a feature that has a class of
// wetland OR wetland_noveg.
// ["in", "class", "wetland", "wetland_noveg"]

// testFilter will be a function that returns a boolean
var testFilter = ff(filter);

// Layer feature that you're testing. Must have type
// and properties keys.
var feature = {
    type: 2,
    properties: {
       class: "street_limited"
       admin_level: 1
    }
};

// will return a boolean based on whether the feature matched the filter
return testFilter(feature);
```

---
_Source: https://npm.io/package/@maptalks/feature-filter · Machine-readable twin of the npm.io package page. Health data is recomputed on every publish._