Igor Paevshik snippet for rxjs post

some.ts

import { Observable, from} from 'rxjs'; 
import { tap } from 'rxjs/operators';

//Similar to native JS 'some' method,
//if at least one value pass predicate emit true, else false

function some(predicate: Function) {
  return function <T>(source: Observable<T>):Observable<Boolean>{
    return new Observable(subscriber => {
      return source.subscribe({
        next(value) {
          if (predicate.call(null,value)) {
            subscriber.next(true);
            subscriber.complete();
          }
        },
        error(error) {
          subscriber.error(error);
        },
        complete() {
          subscriber.next(false);
          subscriber.complete();
        }
      });
    });
  }
}

interface User {
  name: string,
  age: number
}

const users = from([{name: 'John', age: 29}, {name: 'Mike', age:26}]);

users.pipe(
  some((user: User) => user.name === 'Mike')
).subscribe(value => console.log(value));