trezor-suite/packages/address-validator/src/ae_validator.js

const { addressType } = require('./crypto/utils');
var base58 = require('./crypto/base58');

const ALLOWED_CHARS = '123456789ABCDEFGHJKLMNPQRSTUVWXYZabcdefghijkmnopqrstuvwxyz';

var regexp = new RegExp('^(ak_)([' + ALLOWED_CHARS + ']+)$'); // Begins with ak_ followed by

module.exports = {
    isValidAddress: function (address, currency, networkType) {
        let match = regexp.exec(address);
        if (match !== null) {
            return this.verifyChecksum(match[2]);
        } else {
            return false;
        }
    },

    verifyChecksum: function (address) {
        var decoded = base58.decode(address);
        decoded.splice(-4, 4); // remove last 4 elements. Why is base 58 adding them?
        return decoded.length === 32;
    },

    getAddressType: function (address, currency, networkType) {
        if (this.isValidAddress(address, currency, networkType)) {
            return addressType.ADDRESS;
        }
        return undefined;
    },
};