hashtable.js

const PROXY_PREFS_TO_PROPERTIES_MAP = new Map([
  ["network.proxy.autoconfig_url", "automaticProxyConfigUrl"],
  ["signon.autologin.proxy", "autoLogin"],
  ["network.proxy.socks_remote_dns", "proxyDNSForSocks5"],
]);

const getProxyPref = propertyName => {
 return Array.from(
   PROXY_PREFS_TO_PROPERTIES_MAP.entries()).find(entry => entry[1] === propertyName)[0];
};

// Get propertyName for pref:
PROXY_PREFS_TO_PROPERTIES_MAP.get(prefName);

// Get pref for propertyName:
getProxyPref(propertyName);