# @turf/polygonize

# polygonize

Polygonizes [(Multi)LineString(s)](http://geojson.org/geojson-spec.html#linestring) into [Polygons](Polygons).

Implementation of GEOSPolygonize function (`geos::operation::polygonize::Polygonizer`).

Polygonizes a set of lines that represents edges in a planar graph. Edges must be correctly
noded, i.e., they must only meet at their endpoints. (NOTE: while TurfJS has no specific function, an easy way to
ensure this is to use the QGis library and call unaryUnion() on the set of input geometries and then pass the
result to turf-polygonize)

The implementation correctly handles:

-   Dangles: edges which have one or both ends which are not incident on another edge endpoint.
-   Cut Edges (bridges): edges that are connected at both ends but which do not form part of a polygon.

**Parameters**

-   `geojson` **([FeatureCollection](http://geojson.org/geojson-spec.html#feature-collection-objects) \| [Geometry](http://geojson.org/geojson-spec.html#geometry) \| [Feature](http://geojson.org/geojson-spec.html#feature-objects)<([LineString](http://geojson.org/geojson-spec.html#linestring) \| [MultiLineString](http://geojson.org/geojson-spec.html#multilinestring))>)** Lines in order to polygonize


-   Throws **[Error](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Error)** if GeoJSON is invalid.

Returns **[FeatureCollection](http://geojson.org/geojson-spec.html#feature-collection-objects)<[Polygon](http://geojson.org/geojson-spec.html#polygon)>** Polygons created

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---

This module is part of the [Turfjs project](http://turfjs.org/), an open source
module collection dedicated to geographic algorithms. It is maintained in the
[Turfjs/turf](https://github.com/Turfjs/turf) repository, where you can create
PRs and issues.

### Installation

Install this module individually:

```sh
$ npm install @turf/polygonize
```

Or install the Turf module that includes it as a function:

```sh
$ npm install @turf/turf
```