puyopuyotetr.is/app/javascript/mastodon/components/display_name.js

import React from 'react';
import ImmutablePropTypes from 'react-immutable-proptypes';
import PropTypes from 'prop-types';
import { autoPlayGif } from 'mastodon/initial_state';

export default class DisplayName extends React.PureComponent {

  static propTypes = {
    account: ImmutablePropTypes.map.isRequired,
    others: ImmutablePropTypes.list,
    localDomain: PropTypes.string,
  };

  _updateEmojis () {
    const node = this.node;

    if (!node || autoPlayGif) {
      return;
    }

    const emojis = node.querySelectorAll('.custom-emoji');

    for (var i = 0; i < emojis.length; i++) {
      let emoji = emojis[i];
      if (emoji.classList.contains('status-emoji')) {
        continue;
      }
      emoji.classList.add('status-emoji');

      emoji.addEventListener('mouseenter', this.handleEmojiMouseEnter, false);
      emoji.addEventListener('mouseleave', this.handleEmojiMouseLeave, false);
    }
  }

  componentDidMount () {
    this._updateEmojis();
  }

  componentDidUpdate () {
    this._updateEmojis();
  }

  handleEmojiMouseEnter = ({ target }) => {
    target.src = target.getAttribute('data-original');
  }

  handleEmojiMouseLeave = ({ target }) => {
    target.src = target.getAttribute('data-static');
  }

  setRef = (c) => {
    this.node = c;
  }

  render () {
    const { others, localDomain } = this.props;

    let displayName, suffix, account;

    if (others && others.size > 1) {
      displayName = others.take(2).map(a => <bdi key={a.get('id')}><strong className='display-name__html' dangerouslySetInnerHTML={{ __html: a.get('display_name_html') }} /></bdi>).reduce((prev, cur) => [prev, ', ', cur]);

      if (others.size - 2 > 0) {
        suffix = `+${others.size - 2}`;
      }
    } else {
      if (others && others.size > 0) {
        account = others.first();
      } else {
        account = this.props.account;
      }

      let acct = account.get('acct');

      if (acct.indexOf('@') === -1 && localDomain) {
        acct = `${acct}@${localDomain}`;
      }

      displayName = <bdi><strong className='display-name__html' dangerouslySetInnerHTML={{ __html: account.get('display_name_html') }} /></bdi>;
      suffix      = <span className='display-name__account'>@{acct}</span>;
    }

    return (
      <span className='display-name' ref={this.setRef}>
        {displayName} {suffix}
      </span>
    );
  }

}