code: function distanceToNearest(coords, points, distanceType) {
          var color = Infinity,
              distanceFunc = 'distanceTo' + distanceType;
          for (var k = 0; k < points.length; k++) {
              var d = points[k][distanceFunc](coords);
              if (d < color) {
                  color = d;
              }
          }
          return color;
      }
docs: Find the Voronoi centroid closest to the current terrain vertex.
  
  This approach is naive, but since the number of cells isn't typically
  very big, it's plenty fast enough.
  
  Alternatives approaches include using Fortune's algorithm or tracking
  cells based on a grid.