rsa-compat.js/lib/generate-privkey-ursa.js

'use strict';

module.exports = function (bitlen, exp) {
  return require('ursa').generatePrivateKey(bitlen || 2048, exp || 65537).toPrivatePem().toString('ascii').trim();
};

if (require.main === module) {
  console.log(module.exports(2048, 0x10001));
}