I'm trying to create a calling app using flutter and I've created the backend using a node.js. This is how my main.dart file in flutter looks like:

import 'package:flutter/material.dart';
import 'dart:async';
import 'dart:io';
import 'package:flutter/services.dart';
import 'package:flutter_dialpad/flutter_dialpad.dart';

import 'dart:js';
import 'package:js/js.dart';

void main() => runApp(MyApp());

class MyApp extends StatefulWidget {
  @override
  _MyAppState createState() => _MyAppState();
}

class _MyAppState extends State<MyApp> {

  @override
  Widget build(BuildContext context) {
    return MaterialApp(
      home: Scaffold(
        backgroundColor: Colors.black,
        body: SafeArea(
            child:
            DialPad(
                enableDtmf: true,
                outputMask: "(000) 000-0000",
                backspaceButtonIconColor: Colors.red,
                makeCall: (number){
                  print(number);
                }
            )
        ),
      ),
    );
  }
}

I want to use this "number" variable in my app.js file which looks like this:

const accountSid = '***';
const authToken = '***';
const client = require('twilio')(accountSid, authToken);

client.calls.create({
          url: 'http://demo.twilio.com/docs/voice.xml',
         to: '+10000000',
         from: '+1000000',
       }, function(err, call){
           if (err) {
               console.log(err);
           } else {
            console.log(call.sid);
           }
       })

I want to be able to use the "number" variable from my main.dart file in the "to" field in my app.js file. Please help me out...