metamask-extension/shared/constants/tokens.js

import contractMap from '@metamask/contract-metadata';

/**
 * A normalized list of addresses exported as part of the contractMap in
 * `@metamask/contract-metadata`. Used primarily to validate if manually entered
 * contract addresses do not match one of our listed tokens
 */
export const LISTED_CONTRACT_ADDRESSES = Object.keys(
  contractMap,
).map((address) => address.toLowerCase());