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if (window.navigator && window.navigator.msSaveOrOpenBlob) {
  const data = "<base64 string/>"
  const fileName = 'file.pdf'
  const byteCharacters = atob(data)
  
  let byteNumbers = new Array(byteCharacters.length)

  for (var i = 0; i < byteCharacters.length; i++) {
    byteNumbers[i] = byteCharacters.charCodeAt(i)
  }

  const byteArray = new Uint8Array(byteNumbers)
  const blob = new Blob([byteArray], {type: 'application/pdf'})

  window.navigator.msSaveOrOpenBlob(blob, fileName)
}