API in mean stack - node.js

Question

Is it possible to do the following with service in angular6?
How to call api for the following requirement?
1. Mandatory properties check
2. return response code 400 with right message if there is any mandatory check failures
3. data type validations
4. return response code 400 with right message
5. Initialize DB call
6.run DB queries and return response
7. If any errors during the DB call, return reponse code 500 with right message
8.if success then return the response object.
This is something new to me , hence don't know how to implement it. So couldn't try anything .
//blog.service.ts
import { Injectable, Inject, Output, EventEmitter } from '#angular/core';
import { HttpClient, HttpHeaders } from '#angular/common/http';
import { Observable } from 'rxjs';
import { APP_CONFIG, AppConfig } from '../app.config';
import { map } from 'rxjs/operators';
#Injectable({
providedIn: 'root'
})
export class BlogService {
#Output() userLoggedIn: EventEmitter<any> = new EventEmitter();
constructor(private http: HttpClient, #Inject(APP_CONFIG) private _config: AppConfig) { }
////////////////////////////////////////////////////
Save(blogForm: any): Observable<any> {
return Observable.create(observer => {
this.http.post(this._config.apiEndpoint + '/newblog',
JSON.stringify(blogForm), { headers: new HttpHeaders({ 'Content-Type': 'application/json' }) }
)
.subscribe((response: Response) => {
observer.next(response);
observer.complete();
});
});
}
////////////////////////////////////////////////////
allBlogs(): any{
return this.http.get(this._config.apiEndpoint + '/getblogs').pipe(map(response=>response));
}
////////////////////////////////////////////////////
recentBlogs(): any{
return this.http.get(this._config.apiEndpoint + '/get-recent-blogs').pipe(map(response=>response));
}
////////////////////////////////////////////////////
viewBlog(blog_id:number): any{
return this.http.get(this._config.apiEndpoint+'/viewblog/'+blog_id).pipe(map(response=>response));
}
////////////////////////////////////////////////////
datewiseBlogs(year:any,month:any): any{
return this.http.get(this._config.apiEndpoint+'/year-blogs/'+year+'/month/'+month).pipe(map(response=>response));
}
////////////////////////////////////////////////////
deleteblog(blogid): Observable<any> {
return Observable.create(observer => {
this.http.post(this._config.apiEndpoint+'/deleteblog', { _id: blogid }, { headers: new HttpHeaders({ 'Content-Type': 'application/json' }) }
).subscribe((response: Response) => {
observer.next(response);
observer.complete();
});
});
}
////////////////////////////////////////////////////
editblog(blogForm: any): Observable<any> {
return Observable.create(observer => {
this.http.post(this._config.apiEndpoint + '/updateblog',
JSON.stringify(blogForm), { headers: new HttpHeaders({ 'Content-Type': 'application/json' }) }
).subscribe((response: Response) => {
observer.next(response);
observer.complete();
});
});
}
////////////////////////////////////////////////////
}
Expected result is to call the api in the service above and do other operations as listed above.