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

import PureRenderMixin from 'react-addons-pure-render-mixin';

const outerStyle = {
  padding: '15px',
  fontSize: '16px',
  background: '#2f3441',
  flex: '0 0 auto',
  cursor: 'pointer',
  color: '#2b90d9'
};

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

const ColumnBackButton = React.createClass({

  contextTypes: {
    router: React.PropTypes.object
  },

  mixins: [PureRenderMixin],

  handleClick () {
    this.context.router.goBack();
  },

  render () {
    return (
      <div onClick={this.handleClick} style={outerStyle}>
        <i className='fa fa-fw fa-chevron-left' style={iconStyle} />
        Back
      </div>
    );
  }

});

export default ColumnBackButton;