title: How to use config variable in React Native
body: <p>I am new in react-native and haven't use any starter kit.
  my question is how can I use config variables. say for example i have api url which is diffrent for production and development. I don't want to go in each page change url every time.</p>
  
  <p>That's why i want to use something like config variables.</p>
  
  <p>any suggestions ?</p>