# supercluster [](https://github.com/mourner/projects) [](https://travis-ci.org/mapbox/supercluster)
A very fast JavaScript library for geospatial point clustering for browsers and Node.
```html
```
```js
const index = new Supercluster({
radius: 40,
maxZoom: 16
});
index.load(points);
index.getClusters([-180, -85, 180, 85], 2);
```
Clustering 6 million points in Leaflet:
## Install
Install using NPM (`npm install supercluster`) or Yarn (`yarn add supercluster`), then:
```js
// import as a ES module
import Supercluster from 'supercluster';
// or require in Node / Browserify
const Supercluster = require('supercluster');
```
Or use a browser build directly:
```html
```
## Methods
#### `load(points)`
Loads an array of [GeoJSON Feature](https://tools.ietf.org/html/rfc7946#section-3.2) objects. Each feature's `geometry` must be a [GeoJSON Point](https://tools.ietf.org/html/rfc7946#section-3.1.2). Once loaded, index is immutable.
#### `getClusters(bbox, zoom)`
For the given `bbox` array (`[westLng, southLat, eastLng, northLat]`) and integer `zoom`, returns an array of clusters and points as [GeoJSON Feature](https://tools.ietf.org/html/rfc7946#section-3.2) objects.
#### `getTile(z, x, y)`
For a given zoom and x/y coordinates, returns a [geojson-vt](https://github.com/mapbox/geojson-vt)-compatible JSON tile object with cluster/point features.
#### `getChildren(clusterId)`
Returns the children of a cluster (on the next zoom level) given its id (`cluster_id` value from feature properties).
#### `getLeaves(clusterId, limit = 10, offset = 0)`
Returns all the points of a cluster (given its `cluster_id`), with pagination support:
`limit` is the number of points to return (set to `Infinity` for all points),
and `offset` is the amount of points to skip (for pagination).
#### `getClusterExpansionZoom(clusterId)`
Returns the zoom on which the cluster expands into several children (useful for "click to zoom" feature) given the cluster's `cluster_id`.
## Options
| Option | Default | Description |
|----------|---------|-------------------------------------------------------------------|
| minZoom | 0 | Minimum zoom level at which clusters are generated. |
| maxZoom | 16 | Maximum zoom level at which clusters are generated. |
| radius | 40 | Cluster radius, in pixels. |
| extent | 512 | (Tiles) Tile extent. Radius is calculated relative to this value. |
| nodeSize | 64 | Size of the KD-tree leaf node. Affects performance. |
| log | false | Whether timing info should be logged. |
### Property map/reduce options
In addition to the options above, supercluster supports property aggregation with the following three options:
- `map`: a function that returns cluster properties corresponding to a single point.
- `reduce`: a reduce function that merges properties of two clusters into one.
Example of setting up a `sum` cluster property that accumulates the sum of `myValue` property values:
```js
const index = new Supercluster({
map: (props) => ({sum: props.myValue}),
reduce: (accumulated, props) => { accumulated.sum += props.sum; }
});
```
Note that `reduce` must not mutate the second argument (`props`).
## Developing Supercluster
```
npm install # install dependencies
npm run build # generate dist/supercluster.js and dist/supercluster.min.js
npm test # run tests
```