The provider service to manage RPC calls

provider.service.ts

import { Injectable, Inject } from '@angular/core';
import { URL } from './provider.module';

@Injectable({ providedIn: 'root' })
export class Provider {
  private rpcId: number;

  constructor(@Inject(URL) private url: string) {}

  /** JSON RPC Request */
  private req(method: string, params?: any[]) {
    return {
      jsonrpc: '2.0',
      id: this.rpcId,
      method: method,
      params: params || []
    };
  }

  /** Send a request to the node */
  public rpc<T>(method: string, params?: any[]): Observable<T> {
    const payload = this.req(method, params);
    this.rpcId++;
    return this.http.post(this.url, payload).pipe(
      map(res => {
        if (res.error) throw res.error;
        return res.result;
      })
    );
  }

}