AugurProject/augur-ui

// Taken directly from geth's source: https://github.com/ethereum/go-ethereum/blob/aa9fff3e68b1def0a9a22009c233150bf9ba481f/jsre/ethereum_js.go#L2288
// Modified for linting + import only

import { augur } from "services/augurjs";

/**
 * Checks if the given string is an address
 *
 * @method isAddress
 * @param {String} address the given HEX adress
 * @return {Boolean}
 */
export default function isAddress(address) {
  // make sure the address passed has `0x` to start it.
  const formattedAddress = `0x${address.replace("0x", "")}`;
  if (!/^(0x)?[0-9a-f]{40}$/i.test(formattedAddress)) {
    // check if it has the basic requirements of an address
    return false;
  } else if (
    /^(0x)?[0-9a-f]{40}$/.test(formattedAddress) ||
    /^(0x)?[0-9A-F]{40}$/.test(formattedAddress)
  ) {
    // If it's all small caps or all all caps, return true
    return true;
  }

  // Otherwise check each case
  return isChecksumAddress(formattedAddress);
}
/**
 * Checks if the given string is a checksummed address
 *
 * @method isChecksumAddress
 * @param {String} address the given HEX adress
 * @return {Boolean}
 */
function isChecksumAddress(address) {
  // Check each case
  const formattedAddress = address.replace("0x", "");
  const addressHash = augur.rpc.sha3(formattedAddress.toLowerCase());
  for (let i = 0; i < 40; i++) {
    // the nth letter should be uppercase if the nth digit of casemap is 1
    if (
      (parseInt(addressHash[i], 16) > 7 &&
        address[i].toUpperCase() !== address[i]) ||
      (parseInt(addressHash[i], 16) <= 7 &&
        address[i].toLowerCase() !== address[i])
    ) {
      return false;
    }
  }
  return true;
}