quinn/use-supercluster

A React Hook for using Supercluster

useSupercluster

A hook for using Supercluster with React.

const { clusters, supercluster } = useSupercluster({
  points: [],
  bounds: [
    -1.2411810957931664,
    52.61208435908725,
    -1.0083656811012531,
    52.64495957533833
  ],
  zoom: 12,
  options: { radius: 75, maxZoom: 20 }
});

Installation

You will need to install Supercluster as a peer dependency of this package.

yarn add supercluster use-supercluster

Examples

This package contains an example along with tests, but full examples with instructions in the most popular mapping libraries for React can be found below.

Mapbox

Full instructions and an example can be found here.

Google Maps

Full instructions and an example can be found here.

Leaflet

Full instructions and an example can be found here.

Configuration

The last (fourth) argument passed to the useSupercluster hook are options that are passed directly to the instance of Supercluster. You can use any of Supercluster's options.

Map & Reduce Options

As an example, you can use map and reduce to keep track of a total value summed up from across the points. In this case we have the total cost, the max severity, plus another count (which is redundant because Supercluster gives us the point_count property).

const options = {
  radius: 75,
  maxZoom: 20,
  map: props => ({
    cost: props.cost,
    severity: props.severity,
    count: 1
  }),
  reduce: (acc, props) => {
    acc.count += 1;
    acc.cost += props.cost;
    acc.severity = Math.max(acc.severity, props.severity);
    return acc;
  }
};

I found map and reduce a little confusing! The value returned from map of the first point is used as the initial value passed as the accumulator to the reduce function. The only props you have available in reduce are the ones returned from map. You technically don't need to return a value from reduce (it's not used), but instead need to mutate the accumulator object.

Then these accumulated properties can be used and are available on each cluster:

<ul>
  {clusters.map(point => {
    const properties = point.properties || {};
    if (properties.cluster) {
      return (
        <li key={point.id}>
          <h2>Points: {properties.point_count}</h2>
          <p>Cost: {properties.cost.toFixed(2)}</p>
          <p>Severity: {properties.severity}</p>
          <p>Count: {properties.count}</p>
        </li>
      );
    } else {
      return <li key={properties.crimeId}>{properties.category}</li>;
    }
  })}
</ul>