Updating map bounds using react-google-maps

MapComponent.jsx

/* Only the necessary information to address
 * https://github.com/tomchentw/react-google-maps/issues/183#issuecomment-220705977
 * has been included here.
 *
 * YMMV.
 */

import React from 'react';

// Need these to muck around with bounds
import { fitBounds } from 'google-map-react/utils';
import LatLng from 'google-map-react/lib/utils/lib_geo/lat_lng.js';
import LatLngBounds from 'google-map-react/lib/utils/lib_geo/lat_lng_bounds.js';

class Map extends React.Component {
  constructor(props) {
    super(props);

    // State used for the map component
    // You will probably want to build your markers here too on init (see rebuildMarkers)
    this.state = {
      center: {lat: this.props.defaultCenter.lat, lng: this.props.defaultCenter.lng},
      zoom: this.props.defaultZoom,
      bounds: new LatLngBounds()
    };
  }
  
  componentWillReceiveProps(nextProps) {
    if (nextProp.coords) {
      this.rebuildMarkers(nextProp.coords);
    }
  }
  
  rebuildMarkers(coords) {
    let newBounds = new LatLngBounds();
    
    // foreach coord
      // 1. build your marker
      // 2. update your bounds to include the new point
      newBounds.extend(new LatLng(newLat, newLng));
    // end 
    
    this.setState(/* update marker and bounds */);
  }
    
  onBoundsChange({zoom, center}) {
    let state = {};
    // We've been updating the bounds when we rebuild the markers, so use that to update the 
    // map bounds.
    if (this.state.bounds) {
      const geoService = this.refs.map.geoService_;
      const fit = fitBounds(
          {nw: this.state.bounds.getNorthWest(), se: this.state.bounds.getSouthEast()},
          {width: geoService.getWidth(), height: geoService.getHeight()}
      );

      // re-centre
      state = {
        center: fit.center,
        zoom: fit.zoom
      };
    } else {
      state = {
        center,
        zoom
      };
    }
    this.setState(state);
  }
  
  render() {
    return (<div>
      <GoogleMap
          ref="map"
          options={mapOptions}
          zoom={this.state.zoom}
          center={this.state.center}
          onChange={this.onBoundsChange}>
        {markers}
      </GoogleMap>
    </div>);
  }
}

I refactored the rebuildMarkers as commented here.