TypeError: Cannot read properties of undefined (reading 'after') at card.js:20:13

Question

card.js

export class Cards {
  constructor(domain, topic, limit) {
    this.domain = domain;
    this.after = '';
    this.topic = topic;
    this.limit = limit;
  }

  addCards(parentElement) {
    let url = `https://www.${this.domain}.com/r/${this.topic}.json?after=${this.after}&limit=${this.limit}`;

    fetch(url).then(function(response) {
      return response.json();
    })
      .then(function(data) {
        this.after = data.data.after;
        
        let children = data.data.children;
        
        children.map(function(val) {
          let div = document.createElement('div');
          
          div.setAttribute('class', 'card');
          
          let img = document.createElement('img');
          
          img.setAttribute('width', '200');
          img.src = val.data.url;
          div.appendChild(img);
          parentElement.appendChild(div);
        })
      })
      .catch(function(error) {
        console.log(error)
      });
  }
}

main.js

import {
  Cards
} from "./card.js";

// `<div>` Element that contains all cards.
const container = document.querySelector('.container');

// Creating all cards with class Cards.
let memeCards = new Cards('reddit', 'memes', 50);

// Binding Cards to Container.
memeCards.addCards(container);

I’m trying to fetch new images each time I click on a button. That’s the reason why I’ve created the property this.after, but for some reason I get the error “TypeError: Cannot read properties of undefined (reading 'after') at card.js:20:13”.