mastodon/app/javascript/mastodon/features/compose/containers/emoji_picker_dropdown_container.js

import { connect } from 'react-redux';
import EmojiPickerDropdown from '../components/emoji_picker_dropdown';
import { changeSetting } from '../../../actions/settings';
import { createSelector } from 'reselect';
import { Map as ImmutableMap } from 'immutable';
import { useEmoji } from '../../../actions/emojis';

const perLine = 8;
const lines   = 2;

const getFrequentlyUsedEmojis = createSelector([
  state => state.getIn(['settings', 'frequentlyUsedEmojis'], ImmutableMap()),
], emojiCounters => emojiCounters
    .keySeq()
    .sort((a, b) => emojiCounters.get(a) - emojiCounters.get(b))
    .reverse()
    .slice(0, perLine * lines)
    .toArray()
);

const mapStateToProps = state => ({
  custom_emojis: state.get('custom_emojis'),
  autoPlay: state.getIn(['meta', 'auto_play_gif']),
  skinTone: state.getIn(['settings', 'skinTone']),
  frequentlyUsedEmojis: getFrequentlyUsedEmojis(state),
});

const mapDispatchToProps = (dispatch, { onPickEmoji }) => ({
  onSkinTone: skinTone => {
    dispatch(changeSetting(['skinTone'], skinTone));
  },

  onPickEmoji: emoji => {
    dispatch(useEmoji(emoji));

    if (onPickEmoji) {
      onPickEmoji(emoji);
    }
  },
});

export default connect(mapStateToProps, mapDispatchToProps)(EmojiPickerDropdown);