mastodon/app/assets/javascripts/components/features/compose/components/upload_form.jsx

import PureRenderMixin    from 'react-addons-pure-render-mixin';
import ImmutablePropTypes from 'react-immutable-proptypes';
import IconButton         from '../../../components/icon_button';

const UploadForm = React.createClass({

  propTypes: {
    media: ImmutablePropTypes.list.isRequired,
    is_uploading: React.PropTypes.bool,
    onRemoveFile: React.PropTypes.func.isRequired
  },

  mixins: [PureRenderMixin],

  render () {
    const uploads = this.props.media.map(attachment => (
      <div key={attachment.get('id')} style={{ borderRadius: '4px', marginBottom: '10px' }} className='transparent-background'>
        <div style={{ width: '100%', height: '100px', borderRadius: '4px', background: `url(${attachment.get('preview_url')}) no-repeat center`, backgroundSize: 'cover' }}>
          <IconButton icon='times' title='Undo' size={36} onClick={this.props.onRemoveFile.bind(this, attachment.get('id'))} />
        </div>
      </div>
    ));

    return (
      <div style={{ marginBottom: '20px', padding: '10px', overflow: 'hidden' }}>
        {uploads}
      </div>
    );
  }

});

export default UploadForm;