How to catch returned conflict error in react-native?

[ramsestom]

My feathers server is returning a conflict error (when I try to create a new user with a primary key that already exists in the database)
Here is the error I have on the server:

error: (409) Route: /users - E11000 duplicate key error collection: printsServer.users index: email_1 dup key: { : "toto@yahoo.fr" }
info: Conflict: E11000 duplicate key error collection: printsServer.users index: email_1 dup key: { : "toto@yahoo.fr" }
    at Conflict.ExtendableBuiltin (C:\Development\feathers\prints-server\node_modules\feathers-errors\lib\index.js:21:28)
    at Conflict.FeathersError (C:\Development\feathers\prints-server\node_modules\feathers-errors\lib\index.js:99:87)
    at new Conflict (C:\Development\feathers\prints-server\node_modules\feathers-errors\lib\index.js:236:77)
    at errorHandler (C:\Development\feathers\prints-server\node_modules\feathers-mongoose\lib\error-handler.js:34:27)
    at run (C:\Development\feathers\prints-server\node_modules\core-js\modules\es6.promise.js:87:22)
    at C:\Development\feathers\prints-server\node_modules\core-js\modules\es6.promise.js:100:28
    at flush (C:\Development\feathers\prints-server\node_modules\core-js\modules\_microtask.js:18:9)
    at _combinedTickCallback (internal/process/next_tick.js:67:7)
    at process._tickCallback (internal/process/next_tick.js:98:9)

However, when I catch the error in my react-native app with the following code:

   this.app.service('users').create(userData).then((result) => {
         ... do my stuff here
    }).catch((err) => {
      console.log('err');
      console.log(err);
    });

here is the error message I catch (in the console):

I/ReactNativeJS( 7804): err
I/ReactNativeJS( 7804): { [ReferenceError: Can't find variable: Reflect]
I/ReactNativeJS( 7804):   line: 93539,
I/ReactNativeJS( 7804):   column: 21,
I/ReactNativeJS( 7804):   sourceURL: 'http://localhost:8081/index.android.bundle?platform=android&dev=true&hot=false&minify=false' }

Does anyone knows how I can obtain in my react-native app an error message that is usable (that inform me on the actual error, like on the server, and that I can parse and convert to an error message understandable to the user (like: "an account with this email already exists"))

[daffl]

Did you include babel-polyfill or another ES6 polyfill (like core-js) as mentioned in the React Native client guide?

[ramsestom]

No I didn't. I took example from https://github.com/feathersjs/feathers-react-native-chat that doesn't either and didn't see the "important" notice in the tutorial. My bad.
Importing babel-polyfill fixed it. Thanks

[lock]

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