public isloggedin :boolean;

  loginU(e){
   e.preventDefault();
   console.log(e);
    const username = e.target.elements[0].value;
    const password = e.target.elements[1].value;
    console.log(username, password);


   if (username === 'admin' && password === 'admin'){
   console.log(e);
   this.isloggedin = true;
    this.router.navigate(['/dashboard']);
    return this.isloggedin
   } else
   {
   this.loginStatus = 'Invalid Username/Password';

 }
 }

import {LoginComponent} from '../login/login.component';
 constructor private _login: LoginComponent) {
 ngOnInit() {
 console.log("From header " +  this._login.isloggedin)
  }

 <button *ngIf="_login.isloggedin" mat-button (click)="logout()" style="outline:none;margin-left: 5px;float: right;"><i class="material-icons" style="color: white;">
      power_settings_new
      </i></button>