util.js

class Utility {

  static get_data(key) {
    return new Promise(resolve => {
      chrome.storage.local.get(key, item => {
        if (item && item[key]) {
          resolve(item[key]);
        }
        else {
          resolve();
        }
      })
    })
  }

  static set_data(key, data) {
    return new Promise(resolve => {
      chrome.storage.local.get(key, item => {
        if (item && item[key]) {
          const merge_data = Object.assign(item[key], data);
          chrome.storage.local.set({ [key]: merge_data }, () => { resolve() });
        }
        else {
          chrome.storage.local.set({ [key]: data }, () => { resolve() });
        }
      })
    })
  }

  static is_expired(date_string) {
    const today = new Date();
    const expire_day = new Date(date_string);
    return (today > expire_day);
  }

  static get_expire_date(duration) {
    const expire_time = new Date(new Date().getTime() + duration * 24 * 60 * 60 * 1000);
    const mm = expire_time.getMonth() + 1;
    const dd = expire_time.getDate();
    const yy = expire_time.getFullYear();;
    const expire_day = `${mm}/${dd}/${yy}`;
    return expire_day;
  }

  static back_fetch(url){
    return new Promise(resolve => {
    const action = 'fetch_http';
    chrome.runtime.sendMessage({ action, url }, response => {
        resolve(response);
      })
    })
  }
}