How to get data post from blogger api using ionic 5?

Ionic Framework
1

If using Ionic 3:

app.module.ts

import { BrowserModule } from '@angular/platform-browser';
import { ErrorHandler, NgModule } from '@angular/core';
import { IonicApp, IonicErrorHandler, IonicModule } from 'ionic-angular';

import { MyApp } from './app.component';
import { HomePage } from '../pages/home/home';
import { ListPage } from '../pages/list/list';

import { StatusBar } from '@ionic-native/status-bar';
import { SplashScreen } from '@ionic-native/splash-screen';
import { ConstantsProvider } from '../providers/constants/constants';
import { PostPage } from '../pages/post/post';
import { HttpClientModule } from '@angular/common/http';

@NgModule({
  declarations: [
    MyApp,
    HomePage,
    ListPage,
    PostPage
  ],
  imports: [
    BrowserModule,
    IonicModule.forRoot(MyApp),
    HttpClientModule
  ],
  bootstrap: [IonicApp],
  entryComponents: [
    MyApp,
    HomePage,
    ListPage,
    PostPage
  ],
  providers: [
    StatusBar,
    SplashScreen,
    {provide: ErrorHandler, useClass: IonicErrorHandler},
    ConstantsProvider
  ]
})
export class AppModule {}

home.ts

import { Component } from '@angular/core';
import { NavController } from 'ionic-angular';
import { ConstantsProvider } from '../../providers/constants/constants';
import { HttpClient } from '@angular/common/http';
import { PostPage } from '../post/post';


@Component({
  selector: 'page-home',
  templateUrl: 'home.html'
})
export class HomePage {
  title: string;
  posts: any[];
  constructor(private constants: ConstantsProvider, private http: HttpClient, public navCtrl: NavController) {
    http.get('https://www.googleapis.com/blogger/v3/blogs/byurl?key=' + constants.getApiKey() + '&url=' + constants.getUrl())
    .subscribe(data => {
      this.title = data.name;
      this.getPosts(data.posts.selfLink);
      console.log(data);
      });
  }

  getPosts(url: string) {
    this.http.get(url + '?maxResults=80' + '&key=' + this.constants.getApiKey())
      .subscribe(data => {
        this.posts = data.items;
        console.log(this.posts);
      });
  }

  openPost(post) {
    this.navCtrl.push(PostPage, {post: post})
  }
}

post.ts

import { Component } from '@angular/core';
import { IonicPage, NavController, NavParams } from 'ionic-angular';

/**
 * Generated class for the PostPage page.
 *
 * See https://ionicframework.com/docs/components/#navigation for more info on
 * Ionic pages and navigation.
 */

@IonicPage()
@Component({
  selector: 'page-post',
  templateUrl: 'post.html',
})
export class PostPage {
  private post;
  constructor(public navCtrl: NavController, public navParams: NavParams) {
    this.post = navParams.get('post');
    console.log(this.post);
  }

  ionViewDidLoad() {
    console.log('ionViewDidLoad PostPage');
  }

}

if using ionic5:

app.module.ts


import { NgModule } from '@angular/core';
import { BrowserModule } from '@angular/platform-browser';
import { RouteReuseStrategy } from '@angular/router';

import { IonicModule, IonicRouteStrategy } from '@ionic/angular';
import { SplashScreen } from '@ionic-native/splash-screen/ngx';
import { StatusBar } from '@ionic-native/status-bar/ngx';

import { AppComponent } from './app.component';
import { AppRoutingModule } from './app-routing.module';
import { PostPage } from "./post/post.page";
import { HttpClientModule} from '@angular/common/http'
import { PostPageRoutingModule } from './post/post-routing.module';
import { PostPageModule } from './post/post.module';

@NgModule({
  declarations: [AppComponent,],
  entryComponents: [PostPage],
  imports: [
    BrowserModule,
    IonicModule.forRoot(),
    AppRoutingModule,
    HttpClientModule,
    PostPageRoutingModule,
    PostPageModule,
  ],
  providers: [
    StatusBar,
    SplashScreen,
    { provide: RouteReuseStrategy, useClass: IonicRouteStrategy }
  ],
  bootstrap: [AppComponent]
})
export class AppModule {}

folder.page.ts (homepage)

import { Component, OnInit } from '@angular/core';
import { ActivatedRoute, Router } from '@angular/router';
import { ConstantsService } from '../constants.service';
import { HttpClient } from '@angular/common/http';
import { PostPage } from "../post/post.page";
import { NavController } from '@ionic/angular';

@Component({
  selector: 'app-folder',
  templateUrl: './folder.page.html',
  styleUrls: ['./folder.page.scss'],
})
export class FolderPage implements OnInit {
  public folder: string;
  title: string;
  posts: any[];
  constructor(
    private activatedRoute: ActivatedRoute, 
    private constants: ConstantsService, 
    private http: HttpClient,
    private navCtrl: NavController,
    private route: Router)  { 
    this.http.get('https://www.googleapis.com/blogger/v3/blogs/byurl?key=' + constants.getApiKey() + '&url=' + constants.getUrl())
    .subscribe(data => {
      this.title = data.name;
      this.getPosts(data.posts.selfLink);
      console.log(data);
    });
    
  }
  getPosts(url: string) {
    this.http.get(url + '?maxResults=80' + '&key=' + this.constants.getApiKey())
      .subscribe(data => {
        this.posts = data.items;
        console.log(this.posts);
      });
}
  ngOnInit() {
    this.folder = this.activatedRoute.snapshot.paramMap.get('id');
  }
  openPost(post) {
    this.route.navigate(['post', {post:post}])
  }
}

post.page.ts (postpage)


import { Component, OnInit } from '@angular/core';
import { NavController, NavParams } from '@ionic/angular';
import { ActivatedRoute } from '@angular/router';
import { FolderPage } from '../folder/folder.page';

@Component({
  selector: 'app-post',
  templateUrl: './post.page.html',
  styleUrls: ['./post.page.scss'],
})
export class PostPage implements OnInit {
  private post: any;
  constructor(private navCtrl: NavController, private activatedRoute: ActivatedRoute) {
    this.activatedRoute.paramMap.subscribe(params => {
    this.post = params.posts[+params.get('post')];
    console.log(this.post)
  });
   }

  ngOnInit() {
    
  }
  
}

Using ionic 3 there is no problem when loading parts of the post when clicking on it. But, in ionic 5 i get this error:
ERROR TypeError: Cannot read property ‘NaN’ of undefined

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