blob <-> base64

blob_base64.js

var data = "Lorem ipsum dolor sit amet, consectetur adipisicing elit, sed do eiusmod tempor incididunt ut labore et dolore magna aliqua." ;

var blob = new Blob([data], {
    type : "text/plain"
    //type : "text/plain; charset=x-user-defined"
    //type : "text/plain; charset=utf8"
});
blobToBase64(blob, function(b64) {      // convert BLOB to BASE64
    var newBlob = base64ToBlob(b64) ;   // convert BASE64 to BLOB
    $('body').html(blob.size + " != " + newBlob.size) ;
});



// source: http://jsperf.com/blob-base64-conversion
function base64ToBlob(base64) {
        var binary = atob(base64);
        var len = binary.length;
        var buffer = new ArrayBuffer(len);
        var view = new Uint8Array(buffer);
        for ( var i = 0; i < len; i++) {
                view[i] = binary.charCodeAt(i);
        }
        var blob = new Blob([ view ]);
        return blob;
};

function blobToBase64(blob, cb) {
    var reader = new FileReader();
    reader.onload = function() {
      var dataUrl = reader.result;
      var base64 = dataUrl.split(',')[1];
      cb(base64);
    };
    reader.readAsDataURL(blob);
};