Change JavaScript string encoding

At the moment I have a large JavaScript string I'm attempting to write to a file, but in a different encoding (ISO-8859-1). I was hoping to use something like downloadify. Downloadify only accepts normal JavaScript strings or base64 encoded strings.

Because of this, I've decided to compress my string using JSZip which generates a nicely base64 encoded string that can be passed to downloadify, and downloaded to my desktop. Huzzah! The issue is that the string I compressed, of course, is still the wrong encoding.

Luckily JSZip can take a Uint8Array as data, instead of a string. So is there any way to convert a JavaScript string into a ISO-8859-1 encoded string and store it in a Uint8Array?

Alternatively, if I'm approaching this all wrong, is there a better solution all together? Is there a fancy JavaScript string class that can use different internal encodings?

Edit: To clarify, I'm not pushing this string to a webpage so it won't automatically convert it for me. I'm doing something like this:

var zip = new JSZip();
zip.file("genSave.txt", result);

return zip.generate({compression:"DEFLATE"});

And for this to make sense, I would need result to be in the proper encoding (and JSZip only takes strings, arraybuffers, or uint8arrays).

This turned out to be a little more obscure than [the author] had thought, so [the author] ended up rolling [his] own solution. It's not nearly as robust as a proper solution would be, but it'll convert a JavaScript string into windows-1252 encoding, and stick it in a Uint8Array:

var enc = new string_transcoder("windows-1252");
var tenc = enc.transcode(result); //This is now a Uint8Array

You can then either use it in the array like [the author] did:

//Make this into a zip
var zip = new JSZip();   
zip.file("genSave.txt", tenc);   
return zip.generate({compression:"DEFLATE"});

Or convert it into a windows-1252 encoded string using this string encoding library:

var string = TextDecoder("windows-1252").decode(tenc);

To use this function, either use:

<script src="//www.eu4editor.com/string_transcoder.js"></script>

Or include this:

function string_transcoder (target) {

    this.encodeList = encodings[target];
    if (this.encodeList === undefined) {
        return undefined;
    }

    //Initialize the easy encodings
    if (target === "windows-1252") {
        var i;
        for (i = 0x0; i <= 0x7F; i++) {
            this.encodeList[i] = i;          
        }
        for (i = 0xA0; i <= 0xFF; i++) {
            this.encodeList[i] = i;
        }
    }

}

string_transcoder.prototype.transcode = function (inString) {


    var res = new Uint8Array(inString.length), i;


    for (i = 0; i < inString.length; i++) {
        var temp = inString.charCodeAt(i);
        var tempEncode = (this.encodeList)[temp];
        if (tempEncode === undefined) {
            return undefined; //This encoding is messed up
        } else {
            res[i] = tempEncode;
        }
    }

    return res;
};

encodings = {

    "windows-1252": {0x20AC:0x80, 0x201A:0x82, 0x0192:0x83, 0x201E:0x84, 0x2026:0x85, 0x2020:0x86, 0x2021:0x87, 0x02C6:0x88, 0x2030:0x89, 0x0160:0x8A, 0x2039:0x8B, 0x0152:0x8C, 0x017D:0x8E, 0x2018:0x91, 0x2019:0x92, 0x201C:0x93, 0x201D:0x94, 0x2022:0x95, 0x2013:0x96, 0x2014:0x97, 0x02DC:0x98, 0x2122:0x99, 0x0161:0x9A, 0x203A:0x9B, 0x0153:0x9C, 0x017E:0x9E, 0x0178:0x9F}     

};