Authentication to Strava API in ionic 3

Register a API in https://www.strava.com/settings/api

// Install plugin inAppBrowser
$ ionic cordova plugin add cordova-plugin-inappbrowser
$ npm install --save @ionic-native/in-app-browser

// I create a provider, but in this example I will do inside a "page".

// Import inAppBrowser in /pages/login/login.ts
import { InAppBrowser } from '@ionic-native/in-app-browser';

// and the contructor
constructor(
  public iab: InAppBrowser
) {
  this.appKey = '<CLIENT_ID>';
  this.redirectURI = 'http://localhost';
  this.url = 'https://www.strava.com/oauth/authorize?client_id=' + this.appKey + '&redirect_uri=' + this.redirectURI + '&response_type=code&approval_prompt=auto&scope=read_all';
}
  
// In HTML need a button
  <button ion-button large block (click)="login()" class="login">Connect to STRAVA</button>

// The button function
login() {
  doLogin().then((code) => {
    console.log(code);
  });
}

// The login function
doLogin() {
  return new Promise((resolve, reject) => {
    let browser = this.iab.create(this.url, '_blank', 'location=no');
    let listener = browser.on('loadstart').subscribe((event: any) => {

      // Avoid transition pages
      if((event.url.indexOf('oauth/authorize') > -1) || (event.url.indexOf('oauth/accept_application') > -1)){
        return;
      }

      // On unauthorize
      if(event.url.indexOf('?state=&error=access_denied') > -1){
        browser.close();
        alert("You must authorize access to Strava in order to manage your equipment.");
        return;
      }

      // On authorization success
      if(event.url.indexOf(this.redirectURI) > -1 ){
        let token = event.url.split('&')[1].split('=')[1];
        listener.unsubscribe();
        browser.close();
        resolve(token);
      } else {
        reject("Could not authenticate");
      }
    });
  });
}