Use environment variable to point to local server

README.md

@@ -79,13 +79,10 @@ npm start
 
 This will open http://localhost:3000 in your browser. By default, it will use the production backend endpoint. 
 
-To test against the backend running locally, make this change in `app/src/constants.ts`:
+To test against the backend running locally, you can use the environment variable `REACT_APP_LOCAL_SERVER` when you start the app, like this:
 
-```diff
--    export const SERVER_URI = 'https://api.sway-playground.org';
--    // export const SERVER_URI = 'http://0.0.0.0:8080';
-+    // export const SERVER_URI = 'https://api.sway-playground.org';
-+    export const SERVER_URI = 'http://0.0.0.0:8080';
+```sh
+REACT_APP_LOCAL_SERVER=true npm start
 ```
 
 ## Contributing to Sway

app/src/constants.ts

@@ -1,8 +1,8 @@
 export const FUEL_GREEN = '#00f58c';
 
-// TODO: Determine the URL based on the NODE_ENV.
-export const SERVER_URI = 'https://api.sway-playground.org';
-// export const SERVER_URI = 'http://0.0.0.0:8080';
+export const SERVER_URI = process.env.REACT_APP_LOCAL_SERVER
+  ? 'http://0.0.0.0:8080'
+  : 'https://api.sway-playground.org';
 
 export const DEFAULT_SWAY_CONTRACT = `contract;