How to add placeholder image to ion-slides in ionic 3 app?

I want to add placeholder image to my ion-slider before my images are loaded dynamically. Here is my code:

HTML

<div *ngIf="service?.banners" class="home-banners">
        <ion-slides  pager="true"  spaceBetween="5" loop="true" autoplay="3900">
            <ion-slide *ngFor='let value of service.banners'>
                
                 <img src="{{value}}"> 
                </ion-slide>
        </ion-slides>
    </div>

SCSS

.home-banners {
    ion-slides {

        height: 50%; 
        padding-left: 5px;
        padding-right: 5px;
         padding-top: 5px;

    }
}

Solution

If you pursue lazy loading approach you could do something like this below:

add a div wrapper and make its background grey (e.g. skeleton UI) or point it to URL (i used external but you can use an img from local assets)
use attribute binding condition to only set src of actual img if it is active slide or +1 index from it (you can alter conditions you need here)
on load of actual image - set a flag in your data model to keep src intact if the image was already loaded

html template:

<ion-content>
  <div>
    <ion-slides #sliders pager="true" spaceBetween="5">
      <ion-slide *ngFor='let imgItem of images; index as i;'>
        <div class="lazySlide">
          <img class="lazyImage" [src]="(sliders.getActiveIndex() == i || sliders.getActiveIndex() == i-1) || imgItem.loaded? imgItem.source:''" (load)="imgItem.loaded=true">
        </div>
      </ion-slide>
    </ion-slides>
  </div>
</ion-content>

Component code example:

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

@Component({
  selector: 'page-home',
  templateUrl: 'home.html'
})
export class HomePage {

  images: Array<{ loaded: boolean, source: string}> = [
    {
      loaded: false,
      source: "https://placeimg.com/1000/1000/nature"
    },
    {
      loaded: false,
      source: "https://placeimg.com/1000/1000/people"
    },
    {
      loaded: false,
      source: "https://placeimg.com/1000/1000/tech"
    },
    {
      loaded: false,
      source: "https://placeimg.com/1000/1000/architecture"
    },
    {
      loaded: false,
      source: "https://placeimg.com/1000/1000/animals"
    }
  ]

  constructor(
  ) {
  }

}

scss:

page-home {
    .lazyImage {
        width: 100%;
        height: 100%;
    }
    .lazySlide {
        background: url(http://via.placeholder.com/1000x1000);
    }
}