Ionic : how to use Infinite Scroll for displaying contact list

I am using Ionic4 . I am trying to display the phone contact list but the loading time for the list is too slow. I want to use Infinite Scroll but its not working . I am new in ionic so please help me .
My html file code :

<ion-content padding >
      <ion-searchbar (keyup)="SerachContact($event)" ></ion-searchbar>
      <ion-list  *ngFor="let contact of contactlist; let i = index;" >
      <ion-item >
            <ion-icon ios="ios-person" md="md-person"></ion-icon> <b>  {{contact.displayName}}</b>
        <ion-col  size="10">
            <ion-icon item-start  ios="ios-call" md="md-call" ></ion-icon> {{ contact.phoneNumbers[0].value}}

 <ion-infinite-scroll threshold="100px (ionInfinite)="onInfiniteScroll($event)">
          loadingText="Loading more data...">


and my ts file code :

import { Component, OnInit ,ViewChild} from '@angular/core';
import { Router } from '@angular/router';
import { Contacts, Contact, ContactField, ContactName } from '@ionic-native/contacts/ngx';

import {  NavController,IonInfiniteScroll} from '@ionic/angular'; 

import { CallNumber } from '@ionic-native/call-number/ngx';

  selector: 'app-contact',
  templateUrl: './',
  styleUrls: ['./'],
  providers: [Contacts],

export class ContactPage implements OnInit {

 @ViewChild(IonInfiniteScroll) infiniteScroll: IonInfiniteScroll;

  ngOnInit() {

 contactlist: any[];   

   constructor(public navCtrl: NavController,private router: Router, 
     private contacts: Contacts , public callNumber: CallNumber ) {

      this.contacts.find(["displayName", "phoneNumbers"], {multiple: true}).then((contacts) => {
        this.contactlist = contacts;
          this.contactlist.sort(function(a, b) {
             return compareStrings(a.displayName, b.displayName);

onInfiniteScroll(event) {
      setTimeout(() => {
      if (data.length == 1000) { = true;
    }, 500);    

How can I use Infinite Scroll for fast display . please give some idea. thanks in advanced