npm install react-native-list-index-bar --save
import RNListIndexBar from 'react-native-list-index-bar';
_scrollToSelectedIndex = (selectedIndex) => {
if (this._listView) {
this._listView.scrollToIndex({index: selectedIndex, animated: true});
}
}
<RNListIndexBar data={data} onClickIndex={this._scrollToSelectedIndex}/>