Angular 6: Property 'of' does not exist on type 'typeof Observable'

Since RxJS 6 the correct and recommended way of using of() (RxJS 5 in Observable.of()) is this:

import { of } from 'rxjs';

I think this import { of } from 'rxjs/observable/of'; will work only while you have rxjs-compat package installed.

There are some updates in rxjs: ( Its rxjs6)

import { of } from 'rxjs';

It will work only when your app has rxjs-compat package installed

You can import of from rxjs:

import { Observable,of } from 'rxjs';

And simply return of()

 return of({
      lbl_select: 'Select',
    });

So your code will be:

import { Injectable } from '@angular/core';
import { TranslateLoader } from '@ngx-translate/core';
import { Observable, of } from 'rxjs';


@Injectable()
export class MiTranslateLoaderService implements TranslateLoader {

  getTranslation(lang: string): Observable<any> {
    return of({
      lbl_select: 'Select',
    });
  }
}