# @turf/buffer

# buffer

Calculates a buffer for input features for a given radius. Units supported are miles, kilometers, and degrees.

When using a negative radius, the resulting geometry may be invalid if
it's too small compared to the radius magnitude. If the input is a
FeatureCollection, only valid members will be returned in the output
FeatureCollection - i.e., the output collection may have fewer members than
the input, or even be empty.

**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)<any>)** input to be buffered
-   `radius` **[number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)** distance to draw the buffer (negative values are allowed)
-   `units` **\[[string](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String)]** any of the options supported by turf units (optional, default `kilometers`)
-   `steps` **\[[number](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Number)]** number of steps (optional, default `64`)

**Examples**

```javascript
var point = turf.point([-90.548630, 14.616599]);
var buffered = turf.buffer(point, 500, 'miles');

//addToMap
var addToMap = [point, buffered]
```

Returns **([FeatureCollection](http://geojson.org/geojson-spec.html#feature-collection-objects) \| [Feature](http://geojson.org/geojson-spec.html#feature-objects)<([Polygon](http://geojson.org/geojson-spec.html#polygon) \| [MultiPolygon](http://geojson.org/geojson-spec.html#multipolygon))> | [undefined](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/undefined))** buffered features

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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/buffer
```

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

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