metamask-extension/app/scripts/controllers/network/enums.js

const ROPSTEN = 'ropsten'
const RINKEBY = 'rinkeby'
const KOVAN = 'kovan'
const MAINNET = 'mainnet'
const LOCALHOST = 'localhost'

const ROPSTEN_CODE = 3
const RINKEYBY_CODE = 4
const KOVAN_CODE = 42

const ROPSTEN_DISPLAY_NAME = 'Ropsten'
const RINKEBY_DISPLAY_NAME = 'Rinkeby'
const KOVAN_DISPLAY_NAME = 'Kovan'
const MAINNET_DISPLAY_NAME = 'Main Ethereum Network'

const MAINNET_RPC_URL = 'https://mainnet.infura.io/metamask'
const ROPSTEN_RPC_URL = 'https://ropsten.infura.io/metamask'
const KOVAN_RPC_URL = 'https://kovan.infura.io/metamask'
const RINKEBY_RPC_URL = 'https://rinkeby.infura.io/metamask'
const LOCALHOST_RPC_URL = 'http://localhost:8545'

const MAINNET_RPC_URL_BETA = 'https://mainnet.infura.io/metamask2'
const ROPSTEN_RPC_URL_BETA = 'https://ropsten.infura.io/metamask2'
const KOVAN_RPC_URL_BETA = 'https://kovan.infura.io/metamask2'
const RINKEBY_RPC_URL_BETA = 'https://rinkeby.infura.io/metamask2'

const DEFAULT_NETWORK = 'rinkeby'
const OLD_UI_NETWORK_TYPE = 'network'
const BETA_UI_NETWORK_TYPE = 'networkBeta'

module.exports = {
  ROPSTEN,
  RINKEBY,
  KOVAN,
  MAINNET,
  LOCALHOST,
  ROPSTEN_CODE,
  RINKEYBY_CODE,
  KOVAN_CODE,
  ROPSTEN_DISPLAY_NAME,
  RINKEBY_DISPLAY_NAME,
  KOVAN_DISPLAY_NAME,
  MAINNET_DISPLAY_NAME,
  MAINNET_RPC_URL,
  ROPSTEN_RPC_URL,
  KOVAN_RPC_URL,
  RINKEBY_RPC_URL,
  LOCALHOST_RPC_URL,
  MAINNET_RPC_URL_BETA,
  ROPSTEN_RPC_URL_BETA,
  KOVAN_RPC_URL_BETA,
  RINKEBY_RPC_URL_BETA,
  DEFAULT_NETWORK,
  OLD_UI_NETWORK_TYPE,
  BETA_UI_NETWORK_TYPE,
}