example.js

class UsefulSearchesService {
  async init() {
    this.data = await this.fetchData()
  }
  async get(params) {
    setInterval(() => this.handleRefresh(), 0)
    return this.data[params]
  }
  async handleRefresh() {
    if (this.shouldRefresh()) {
      try {
        this.data = await this.fetchData()
      }
      catch(e) {
        // log error
      }
    }
}

const services = {}

// called on server startup, so the server fails to start if we can't get the data we need
export async function init(languages) {
  for (language in languages) {
    const service = new UsefulSearchesService()
    await service.init()
    services[language] = service
  }
}

export function getUsefulSearches(language) {
  return services[language]
}
  
// alternative, simpler version that loads/reloads on get
class LazyUsefulSearchesService {
  async get(params) {
    await this.init()
    return this.data[params]
  }
  async init() {
    if (!this.data || this.shouldRefresh()) {
      this.data = this.fetchData()
    }
  }
}