## point in polygon for Leaflet

[![build status](https://secure.travis-ci.org/mapbox/leaflet-pip.png)](http://travis-ci.org/mapbox/leaflet-pip)

A [Leaflet](http://leafletjs.com/)-friendly API for [point in polygon](http://en.wikipedia.org/wiki/Point_in_polygon)
operations, using [substack](https://github.com/substack)'s
[point in polygon](https://github.com/substack/point-in-polygon) library.

## install

With browserify

    npm install leaflet-pip

Resolve for a CDN/packaged version:

    https://unpkg.com/leaflet-pip@latest/leaflet-pip.js

## example

```
var gjLayer = L.geoJson(statesData);
var results = leafletPip.pointInLayer([-88, 38], gjLayer);
// results is an array of L.Polygon objects containing that point
```

## api

### `leafletPip.pointInLayer(point, layer L.GeoJSON, [first])`

Point can be:

* A two-element array of `[lng, lat]`
* A `L.LatLng` object

Layer must be:

* A `L.geoJSON` layer

`first` can be:

* `boolean`: `true` to accept the first match, or `false` to return all
  polygons containing this point. This can be useful if you know that your
  polygons are non-overlapping or don't care about more than one result,
  since it will be much faster. By default, **this is false** and all matches
  are returned.

Returns:

An array of polygons in which the given point resides, an empty array if there
are none. The polygons are returned as direct sublayers, so they can include
MultiPolygons. You can call `pointInLayer` again on those if you want the
sub-polygon result.

### `leafletPip.bassackwards`

Leaflet treats literate coordinate arrays as `[lat, lon]`, unlike GeoJSON
and [any true scotsman](http://en.wikipedia.org/wiki/No_true_Scotsman). `leaflet-pip`
treats literate coordinate arrays as `[lon, lat]`, but if you set `bassackwards`
to true, it'll do things the Leaflet/Google Maps API way.