mastodon/app/assets/javascripts/components/components/column_back_button.jsx

import { FormattedMessage } from 'react-intl';
import PropTypes from 'prop-types';

const iconStyle = {
  display: 'inline-block',
  marginRight: '5px'
};

class ColumnBackButton extends React.PureComponent {

  constructor (props, context) {
    super(props, context);
    this.handleClick = this.handleClick.bind(this);
  }

  handleClick () {
    if (window.history && window.history.length === 1) this.context.router.push("/");
    else this.context.router.goBack();
  }

  render () {
    return (
      <div role='button' tabIndex='0' onClick={this.handleClick} className='column-back-button'>
        <i className='fa fa-fw fa-chevron-left' style={iconStyle} />
        <FormattedMessage id='column_back_button.label' defaultMessage='Back' />
      </div>
    );
  }

};

ColumnBackButton.contextTypes = {
  router: PropTypes.object
};

export default ColumnBackButton;