How to get the ZIP file from Base64 string in Javascript?

Question

I am trying to get the compressed ZIP file back in Javascript. I am able to convert the zip file into Base64 String format. (Zip file is in Server)

Here is my try (at Server Side)

System.IO.FileStream fs = new System.IO.FileStream(SourceFilePath + "Arc.zip", System.IO.FileMode.Open);
Byte[] zipAsBytes = new Byte[fs.Length];
fs.Read(zipAsBytes, 0, zipAsBytes.Length);
String base64String = System.Convert.ToBase64String(zipAsBytes, 0, zipAsBytes.Length);
fs.Close();

if (zipAsBytes.Length > 0)
{
    _response.Status = "ZipFile";
    _response.Result = base64String;
}

return _json.Serialize(_response);

This part of code returns the JSON data. This JSON data includes the Base64 string. Now what i want to do is to get the original zip file from Base64 string. I searched over the internet but not get the idea.

Is this achievable ?.

`System.IO.FileStream fs = new System.IO.FileStream(SourceFilePath + "Arc.zip", System.IO.FileMode.Open);` <-- That does not look like JavaScript. — Cerbrus, Jul 02 '14 at 13:41
What do you man by the get the original zip file? Do you want to extract the contents in the browser? or Store the data as a zip file locally? — levi, Jul 02 '14 at 13:48
@Cebrus: The code i posted here is the try at Server Side. Base64 conversion of ZIP file. — Prabhu Easwar, Jul 02 '14 at 13:52
@levi: second question is the preferred one. I just want to store the zip file in local device. For future use. — Prabhu Easwar, Jul 02 '14 at 13:54
For future use by your JavaScript? or by the user? you would need to put the content into local storage else how would you access it through a script? How big is the uncompressed data? — Alex K., Jul 02 '14 at 13:57
in that case, than why send it as Base64 Json? You can just download the zip directly. See - http://stackoverflow.com/questions/6668776/download-file-through-an-ajax-call-php — levi, Jul 02 '14 at 13:58
The zip file is later on used by the JS functions. If the time come to use then that Base64 string is need to convert to the ZIP file. ( JS use the content inside the zip). Once used then zip file will be getting deleted. — Prabhu Easwar, Jul 02 '14 at 14:06

score 3 · Answer 1 · answered Jul 02 '14 at 14:37

It is achievable. First you must convert the Base64 string to an Arraybuffer. Can be done with this function:

function base64ToBuffer(str){
    str = window.atob(str); // creates a ASCII string
    var buffer = new ArrayBuffer(str.length),
        view = new Uint8Array(buffer);
    for(var i = 0; i < str.length; i++){
        view[i] = str.charCodeAt(i);
    }
    return buffer;
}

Then, using a library like JSZip, you can convert the ArrayBuffer to a Zip file and read its contents:

var buffer = base64ToBuffer(str);
var zip = new JSZip(buffer);
var fileContent = zip.file("someFileInZip.txt").asText();

score -1 · Answer 2 · answered Jul 02 '14 at 13:43

JavaScript does not have that functionality.
Theoretically there can be some js library that does this, but it's size probably would be bigger than the original text file itself.
You can also enable gzip compression on your server, so that any output text gets compressed. Most of the browsers would then uncompress the data upon its arrival.

How to get the ZIP file from Base64 string in Javascript?

2 Answers2