Create Certs with forge npm module. Reference: https://github.com/digitalbazaar/forge#x509

create_certs.js

var forge = require("node-forge");

var pki = forge.pki;
var asn1 = forge.asn1;

// generate a keypair and create an X.509v3 certificate
var keys = pki.rsa.generateKeyPair(2048);

var cert = pki.createCertificate();

cert.publicKey = keys.publicKey;

cert.serialNumber = '01';

cert.validity.notBefore = new Date();
cert.validity.notAfter = new Date();
cert.validity.notAfter.setFullYear(cert.validity.notBefore.getFullYear() + 1);

var attrs = [{
  name: 'commonName',
  value: 'example.org'
}, {
  name: 'countryName',
  value: 'US'
}, {
  shortName: 'ST',
  value: 'Virginia'
}, {
  name: 'localityName',
  value: 'Blacksburg'
}, {
  name: 'organizationName',
  value: 'Test'
}, {
  shortName: 'OU',
  value: 'Test'
}];
cert.setSubject(attrs);

cert.setIssuer(attrs);

cert.setExtensions([{
  name: 'basicConstraints',
  cA: true
}, {
  name: 'keyUsage',
  keyCertSign: true,
  digitalSignature: true,
  nonRepudiation: true,
  keyEncipherment: true,
  dataEncipherment: true
}, {
  name: 'extKeyUsage',
  serverAuth: true,
  clientAuth: true,
  codeSigning: true,
  emailProtection: true,
  timeStamping: true
}, {
  name: 'nsCertType',
  client: true,
  server: true,
  email: true,
  objsign: true,
  sslCA: true,
  emailCA: true,
  objCA: true
}, {
  name: 'subjectAltName',
  altNames: [{
    type: 6, // URI
    value: 'http://example.org/webid#me'
  }, {
    type: 7, // IP
    ip: '127.0.0.1'
  }]
}, {
  name: 'subjectKeyIdentifier'
}]);

cert.sign(keys.privateKey);

// convert a Forge certificate to PEM
var pem = pki.certificateToPem(cert);

console.log(pem)
// convert a Forge certificate from PEM
var cert = pki.certificateFromPem(pem);

// convert an ASN.1 X.509x3 object to a Forge certificate
var inAsn1 = pki.certificateToAsn1(cert);
var inDer = asn1.toDer(inAsn1);
var outAsn1 = asn1.fromDer(inDer);
var outCert = pki.certificateFromAsn1(outAsn1);

// convert a Forge certificate to an ASN.1 X.509v3 object
var asn1Cert = pki.certificateToAsn1(outCert);