Example of app-wide fullScreen style and StyleSheet's built-in absoluteFillObject that does the same thing

ApplicationStyles.js

// App/Theme/ApplicationStyles.js

export default {
  fullScreen: {
    position: 'absolute',
    top: 0,
    bottom: 0,
    left: 0,
    right: 0
  }
}

Colors.js

// App/Theme/ApplicationStyles.js

export default {
  red: '#BD3760',
  reallyFadedWhite: 'rgba(255, 255, 255, 0.3)',
  transparent: 'rgba(0,0,0,0)'
};

index.js

// App/Theme/index.js

import ApplicationStyles from './ApplicationStyles';
import Colors from './Colors';

export default {
  ApplicationStyles,
  Colors
}

styles.js

// App/Components/SomeComponent/styles.js

import { StyleSheet } from 'react-native';
import { ApplicationStyles, Colors } from '../../Theme';

export default StyleSheet.create({
  container: {
    // ...ApplicationStyles.fullScreen,
    ...StyleSheet.absoluteFillObject,
    backgroundColor: Colors.red
  }
});