Helper functions to deal with web push encryption stuff

web-push-subscription-helpers.js

function generateKey(keyName, subscription) {
  var rawKey;
  rawKey = subscription.getKey ? subscription.getKey(keyName) : '';
  return rawKey ?
      btoa(String.fromCharCode.apply(null, new Uint8Array(rawKey))) :
      '';
}

export function generatePublicKey(subscription) {
  return Promise.resolve(generateKey('p256dh', subscription));
}

export function generateAuthKey(subscription) {
  return Promise.resolve(generateKey('auth', subscription));
}

export function urlBase64ToUint8Array(base64String) {
  const padding = '='.repeat((4 - base64String.length % 4) % 4);
  const base64 = (base64String + padding)
    .replace(/\-/g, '+')
    .replace(/_/g, '/');
  const rawData = window.atob(base64);
  const outputArray = new Uint8Array(rawData.length);
  for (let i = 0; i < rawData.length; ++i) {
    outputArray[i] = rawData.charCodeAt(i);
  }
  return outputArray;
}