How to get Base64..?

i have barcode object..
Barcode {
  barcode: { createCode: [Function] },
  options:
   { data: '*282*',
     width: 400,
     height: 100,
     barcolor: '#000',
     bgcolor: '#FFF',
     w: 400,
     h: 100,
     type: 'PNG' } }