use local storage after success full login then set success response like

response: 

let data ={
"email":demo@gmail.com,
"id":1
}
localStograge.setItem("user-data",JSON.stringify(data));

then check ngOnInit function local storage exist or is null

ngOnInit(){
   if(localStograge.setItem("user-data") && JSON.Parse(localStograge.setItem("user-data")).id){
      // manage if condition
   }else{
     // manage else condition
  }
}