Check for web worker Crypto API support

crypto-webworker-support-check.js

// Checks if the global.crypto API is supported inside web workers.
// Uses a serialized function inside a Blob URL to run a web worker
// without an external file. 
// See https://medium.com/@roman01la/run-web-worker-with-a-function-rather-than-external-file-303add905a0

function checkCryptoWorkerSupport() {
  return new Promise((resolve) => {
    const checkFn = () => {
      const cryptoSupported = self.crypto && self.crypto.getRandomValues
      postMessage(!!cryptoSupported)
      self.close()
    }
    const worker = new Worker(URL.createObjectURL(new Blob(['(' + checkFn + ')()'])))
    worker.onmessage = (event) => {
      resolve(event.data.toString() === 'true')
    }
    worker.onerror = (err) => {
      err.preventDefault()
      resolve(false)
    }
  }).then((result) => {
    return result
  }).catch((error) => {
    console.log(`Error when checking for crypto in worker support: ${error}`)
    return false
  })
}