How to use a boolean in a if else statement in react-native [duplicate]

What I'm trying to do is use data from another component in my if-else statement.

This is my class screen:

class Restaurant {
constructor(
    id,
    Categoryids,
    name,
    time,
    km,
    ImageUrl,
    recommended,
    fav,


) {
    this.id = id;
    this.Categoryids = Categoryids;
   this.recommended = recommended;
  //more this....

}
  }

  export default Restaurant;

I have a dummy data component that has all the data for each section. For the recommended, I wrote the data as 'true' or 'false'. And if I understand correctly, this would make them a boolean.

For my homepage which is where I want to output the component, I did:

import React from 'react';
import { StyleSheet, Text, View, Button, Image, ScrollView, FlatList, 
TouchableOpacity, Platform } from 'react-native';
import { FAVORITE, RESTAURANT } from '../extra/dummy-data';
import Homedesign from '../Components/Homedesign';
import HeaderButton from '../Components/HeaderButton';
import { HeaderButtons, Item } from 'react-navigation-header-buttons';
import MealItem from '../Components/MealItem'

const Homepage = props => {
  const renderMealItem = itemData => {
    if (RESTAURANT.recommended === 'true') {
  return (
    <MealItem
      name={itemData.item.name}
      image={itemData.item.imageUrl}
      time={itemData.item.time}
      km={itemData.item.km}
      onSelectMeal={() => {
        props.navigation.navigate({
          routeName: 'MealDetail',
          params: {
            RestaurantId: itemData.item.id
          }
        });
      }}
    />
  );

}


  }

  const favId = props.navigation.getParam('favoriteId');

  const displayedRestaurant = RESTAURANT.filter(
    Restaurant => Restaurant.Categoryids.indexOf(favId) >= 0
  )
  return (
<View style={styles.screen}>
  <FlatList
    data={displayedRestaurant}
    renderItem={renderMealItem}
    style=

  />
</View>
  );
};

I assumed that for this to work we would use an if-else statement.