Can JavaScript Compress JSON Data Client-Side for Servers with Fixed-Size Caches?

JavaScript Implementation of Gzip

Question:

Is there a way to compress JSON data on the client side before sending it to a server with a fixed-size cache?

Answer:

Edit: For better results, use the improved LZW solution found at http://pieroxy.net/blog/pages/lz-string/index.html.

Original Solution:

While JavaScript does not provide an implementation of Gzip, the jsolait library offers functions for LZW compression and decompression. Here is the code:

LZW Compression Function:

function lzw_encode(s) {
    var dict = {};
    var data = (s + "").split("");
    var out = [];
    var currChar;
    var phrase = data[0];
    var code = 256;
    for (var i = 1; i < data.length; i++) {
        currChar = data[i];
        if (dict[phrase + currChar] != null) {
            phrase += currChar;
        } else {
            out.push(phrase.length > 1 ? dict[phrase] : phrase.charCodeAt(0));
            dict[phrase + currChar] = code;
            code++;
            phrase = currChar;
        }
    }
    out.push(phrase.length > 1 ? dict[phrase] : phrase.charCodeAt(0));
    for (var i = 0; i < out.length; i++) {
        out[i] = String.fromCharCode(out[i]);
    }
    return out.join("");
}

LZW Decompression Function:

function lzw_decode(s) {
    var dict = {};
    var data = (s + "").split("");
    var currChar = data[0];
    var oldPhrase = currChar;
    var out = [currChar];
    var code = 256;
    var phrase;
    for (var i = 1; i < data.length; i++) {
        var currCode = data[i].charCodeAt(0);
        if (currCode < 256) {
            phrase = data[i];
        } else {
            phrase = dict[currCode] ? dict[currCode] : (oldPhrase + currChar);
        }
        out.push(phrase);
        currChar = phrase.charAt(0);
        dict[code] = oldPhrase + currChar;
        code++;
        oldPhrase = phrase;
    }
    return out.join("");
}

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