on refresh how to stay on same route in angular6? - angular6

Question

in my code two components are present.
1)app component
2)login component
after login it is going to another page.but on refresh it comes to login page.please solve this issue.i am using angular6.please provide code how to solve this problem.
app.module.ts
--------------------------------
import { BrowserModule } from '#angular/platform-browser';
import { NgModule } from '#angular/core';
import { AppRoutingModule } from './app-routing.module';
import { AppComponent } from './app.component';
import { PloginComponent } from './plogin/plogin.component';
import { AfterploginComponent } from './afterplogin/afterplogin.component';
import { RouterModule } from '#angular/router';
import { ReactiveFormsModule } from '#angular/forms';
import { HttpClientModule } from '#angular/common/http';
#NgModule({
declarations: [
AppComponent,
PloginComponent,
AfterploginComponent
],
imports: [
BrowserModule,
AppRoutingModule,
ReactiveFormsModule,
HttpClientModule,
RouterModule.forRoot([
{
path : 'after-login',
component : AfterploginComponent
},
{
path : 'before-login',
component : PloginComponent
}
])
],
providers: [],
bootstrap: [AppComponent]
})
export class AppModule { }
app.component.ts
-------------------------------------------------
import { Component ,OnInit} from '#angular/core';
import { Router} from '#angular/router';
#Component({
selector: 'app-root',
templateUrl: './app.component.html',
styleUrls: ['./app.component.css']
})
export class AppComponent implements OnInit{
title = 'login';
constructor(private router :Router){
}
ngOnInit(){
this.router.navigateByUrl('before-login');
}
}
i am beginer to angular6.on refresh how to stay on same page i don't know.
plese tell me the different approaches to solve the problem easily.