how to active side menu in ionic3

import { Component, ViewChild } from '@angular/core';

import { Nav, Platform, AlertController, MenuController, Icon }
from 'ionic-angular';

import { StatusBar } from '@ionic-native/status-bar';

import { SplashScreen } from '@ionic-native/splash-screen';

import { HomePage } from '../pages/home/home';

import { WelcomePage } from '../pages/welcome/welcome';

import { Storage } from '@ionic/storage';

import { NetworkInterface } from '@ionic-native/network-interface';

import { Network } from '@ionic-native/network';

import { ChangepasswordPage } from '../pages/changepassword/changepassword';

@Component({

templateUrl: 'app.html'

})

export class MyApp {

@ViewChild(Nav) nav: Nav;

rootPage: any;

pages: Array<{title: string,icon: string, component: any}>;

closelogin: boolean;

user: string;

username: string;

activepage: any;

constructor(public platform: Platform,
public network: Network,

private networkInterface: NetworkInterface,
public menu: MenuController,
public alertController: AlertController,
public statusBar: StatusBar,
public storage: Storage,
public splashScreen: SplashScreen) {

this.initializeApp();

// used for an example of ngFor and navigation

this.pages = [

{ title: 'Home',icon:'ios-home', component: HomePage },

{ title: 'Change Password', icon:'ios-create', component: "ChangepasswordPage" }

];

this.activepage= this.pages[0];

}

initializeApp() {

this.platform.ready().then(() => {

// Okay, so the platform is ready and our plugins are available.

// Here you can do any higher level native things you might need.

this.statusBar.styleDefault();

this.user=localStorage.getItem("loginfieldstaffpramann");

if(this.user=='"YES"')

{

this.rootPage=HomePage;}

else

{

this.rootPage="WelcomePage";

}

this.splashScreen.hide();

});

}

openPage(page) {

// Reset the content nav to have just this page

// we wouldn't want the back button to show in this scenario

this.nav.setRoot(page.component);

this.activepage= page;

this.menu.close();

}

ngOnInit() {

if (localStorage.getItem("loginfieldstaffpramann") == '"YES"') {

debugger;

this.closelogin = false;

}

}

checkNewUserActive(page) {

this.username = "FieldStaff";

return page == this.activepage;

}

logout() {

this.menu.swipeEnable(false);

let alert = this.alertController.create({

title: 'Logout?',

message: 'Are you sure you want to logout?',

buttons: [{

text: 'No'

}, {

text: 'Yes',

handler: () => {

this.storage.clear();

localStorage.setItem("loginfieldstaffpramann", JSON.stringify("NO"));

this.nav.setRoot("WelcomePage");

window.location.reload();

}

}]

});

alert.present();

}

}

<div *ngIf="!closelogin">

<ion-menu [content]="content" side="left" id="field_staff_menu" >

<ion-header>

<ion-toolbar color="pramaan">

<img class="menu-user-image" src="assets/imgs/logo_big.png">

<div class="font18" text-center>Welcome {{username}}</div>

</ion-toolbar>

</ion-header>

<ion-content>

<ion-list no-lines>

<button [class.activeHighlight] ="checkNewUserActive(p)"

ion-item *ngFor="let p of pages" (click)="openPage(p)">

<ion-icon name="{{p.icon}}" width="30"></ion-icon>

{{p.title}}

</button>

<button ion-item (click)="logout()">

<ion-icon name="ios-log-out-outline"></ion-icon>

Logout

</button>

</ion-list>

</ion-content>

</ion-menu>

</div>

<ion-nav [root]="rootPage" #content></ion-nav>

.activeHighlight{

color: #357CA5;

font-weight: 500 !important;

}

https://www.joshmorony.com/create-a-menu-with-active-page-highlight-in-ionic-2/