npm install jks-js

...
const jks = require('jks-js');

const keystore = jks.toPem(
	fs.readFileSync('keystore.jks'),
	'password'
);

const { cert, key } = keystore['alias'];

tls.connect('<port>', '<host>', {
	key: key,
	cert: cert,
});

const {
	/**
	 * Extracts certificates from java keystore or truststore
	 * and decrypts private key 
	 * 
	 * @param keystore content of java keystore or truststore file
	 * @param keystorePassword password for verification and decryption
	 * @param pemPassword (optional) password that is used for decryption, in case it is different from keystorePassword. If not specified, keystorePassword is used
	 * @return {
	 *     <alias name>: {
	 *         cert: string // compound certificates chain
	 *         key: string // decrypted private key 
	 *     } | {
	 *         ca: string // trusted certificate
	 *     }
	 * }
	 */
	toPem,

	/**
	 *  Only extracts certificates
	 *  @param keystore
	 *  @param keystorePassword
	 *  @param pemPassword
	 *  @return { <alias name>: KeyEntry | TrustedKeyEntry }
	 */
	parseJks,

	/**
	 * Decrypts private key from DER to PEM
	 *
	 * @param protectedPrivateKey DER encoded private key
	 * @param password password for PKCS8 decryption
	 * @return decoded private key 
	 */
	decrypt
} = require('jks-js');