metamask-extension/ui/app/helpers/constants/common.js

export const ETH = 'ETH'
export const GWEI = 'GWEI'
export const WEI = 'WEI'

export const PRIMARY = 'PRIMARY'
export const SECONDARY = 'SECONDARY'

export const NETWORK_TYPES = {
  KOVAN: 'kovan',
  MAINNET: 'mainnet',
  RINKEBY: 'rinkeby',
  ROPSTEN: 'ropsten',
  GOERLI: 'goerli',
}