react-native-status-bar-size

var MyApp = React.createClass({
   getInitialState: function() {
     return {
       currentStatusBarHeight: StatusBarSizeIOS.currentHeight,
     };
   },
 
   componentDidMount: function() {
     StatusBarSizeIOS.addEventListener('willChange', this._handleStatusBarSizeWillChange);
     StatusBarSizeIOS.addEventListener('didChange', this._handleStatusBarSizeDidChange);
   },
 
   componentWillUnmount: function() {
     StatusBarSizeIOS.removeEventListener('willChange', this._handleStatusBarSizeWillChange);
     StatusBarSizeIOS.removeEventListener('didChange', this._handleStatusBarSizeDidChange);
   },
 
   _handleStatusBarSizeWillChange: function(nextStatusBarHeight) {
     console.log('Will Change: ' + nextStatusBarHeight);
   },
 
   _handleStatusBarSizeDidChange: function(currentStatusBarHeight) {
     console.log('changed');
     this.setState({ currentStatusBarHeight: currentStatusBarHeight });
   },
 
   render: function() {
     return (
       <View style={{flex: 1, backgroundColor: 'white', justifyContent: 'center', alignItems: 'center'}}>
         <Text>Current status bar height is: {this.state.currentStatusBarHeight}</Text>
       </View>
     );
   },
});