Some class to get user Config from API in a browser

config.js

class Config {
  endpoint = 'https://somewebsite.com/config';

  constructor(userId) {
    this.userId = userId;
  }

  async getValueFor(key) {
    if (this.data) {
      // getting from cache
      return this.data[key];
    }

    return await fetch(`${this.endpoint}/${this.userId}`)
        .then((response) => response.json())
        .then((data) => {
          this.data = data;
          return this.data[key];
        });
  }
}