React-native shadow not appearing

For iOS, raise the zIndex of your outer <View>

const styles = StyleSheet.create({  
 shadow: {  
  shadowOffset: { width: 10, height: 10 },  
  shadowColor: 'black',  
  shadowOpacity: 1,  
  elevation: 3,  
  zIndex:999,  
}  

Is the shadow working on IOs ? Android and IOS work ≠ in React-Native. For android, it works with elevation.

const styles = StyleSheet.create({
shadow: {
  shadowOffset: { width: 10, height: 10 },
  shadowColor: 'black',
  shadowOpacity: 1,
  elevation: 3,
  // background color must be set
  backgroundColor : "#0000" // invisible color
}

Otherwise, try to set a background color to your shadow component :)