如何从Javascript中的Base64字符串获取ZIP文件？

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 ?.

Answer 1

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();

Answer 2

• 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.