text: import React from "react";
  import styled from "styled-components";
  import {
      Button,
      Header,
      Left,
      Right,
      Body,
      Title
  } from "native-base";
  import Icon from "react-native-vector-icons/FontAwesome";
  import FeatherIcon from "react-native-vector-icons/Feather";
  
  const AppIcon = styled(Icon)`
      font-size: 22;
      color: #fff;
  `;
  const BackIcon = styled(FeatherIcon)`
      font-size: 22;
      color: #fff;
  `;
  
  export default props => (<Header>
      <Left>
          {props.back
              ? <Button iconLeft transparent onPress={props.onBack}>
                  <BackIcon name="arrow-left" />
              </Button>
              : <AppIcon name="hacker-news" />}
      </Left>
      <Body>
          <Title>HN Reader</Title>
      </Body>
      <Right />
  </Header>);
  