generate-vapid-keys created by pladaria - https://repl.it/@pladaria/generate-vapid-keys

index.js

const crypto = require('crypto');
const urlBase64 = require('urlsafe-base64');

function generateVAPIDKeys() {
  const curve = crypto.createECDH('prime256v1');
  curve.generateKeys();

  return {
    publicKey: urlBase64.encode(curve.getPublicKey()),
    privateKey: urlBase64.encode(curve.getPrivateKey())
  };
}

console.log(JSON.stringify(generateVAPIDKeys(), null, 2));

package-lock.json

{
  "requires": true,
  "lockfileVersion": 1,
  "dependencies": {
    "urlsafe-base64": {
      "version": "1.0.0",
      "resolved": "https://registry.npmjs.org/urlsafe-base64/-/urlsafe-base64-1.0.0.tgz",
      "integrity": "sha1-I/iQaabGL0bPOh07ABac77kL4MY="
    }
  }
}