google-map-react/develop/markers/ClusterMarker.js

import React from 'react';
import { Motion, spring } from 'react-motion';
import { compose, defaultProps, withPropsOnChange, pure } from 'recompose';

import clusterMarkerStyles from './ClusterMarker.sass';

export const clusterMarker = (
  {
    styles,
    text,
    hovered,
    $hover,
    defaultMotionStyle,
    motionStyle,
  }
) => (
  <Motion defaultStyle={defaultMotionStyle} style={motionStyle}>
    {({ scale }) => (
      <div
        className={styles.marker}
        style={{
          transform: `translate3D(0,0,0) scale(${scale}, ${scale})`,
          zIndex: hovered || $hover ? 1 : 0,
        }}
      >
        <div className={styles.text}>
          {text}
        </div>
      </div>
    )}
  </Motion>
);

export const clusterMarkerHOC = compose(
  defaultProps({
    text: '0',
    styles: clusterMarkerStyles,
    initialScale: 0.6,
    defaultScale: 1,
    hoveredScale: 1.15,
    hovered: false,
    stiffness: 320,
    damping: 7,
    precision: 0.001,
  }),
  // pure optimization can cause some effects you don't want,
  // don't use it in development for markers
  pure,
  withPropsOnChange(['initialScale'], ({
    initialScale,
    defaultScale,
    $prerender,
  }) => ({
    initialScale,
    defaultMotionStyle: { scale: $prerender ? defaultScale : initialScale },
  })),
  withPropsOnChange(['hovered', '$hover'], ({
    hovered,
    $hover,
    hoveredScale,
    defaultScale,
    stiffness,
    damping,
    precision,
  }) => ({
    $hover,
    hovered,
    motionStyle: {
      scale: spring(hovered || $hover ? hoveredScale : defaultScale, {
        stiffness,
        damping,
        precision,
      }),
    },
  }))
);

export default clusterMarkerHOC(clusterMarker);