Proxy server, serving a local file

index.js

var mime = require('mime');

function serveLocalFile (httpRequest, httpResponse, filename) {
    console.log("local: " + httpRequest.url);

    var send404 = function () {
        httpResponse.setHeader('Content-Type', 'text/html');
        httpResponse.write("NOT FOUND: " + httpRequest.url);
        httpResponse.end();
    };

    var existsCallback = function (exists) {
        var readStream;
        if (!exists) {
            send404();
            return;
        }
        httpResponse.setHeader('Content-Type', 
            mime.lookup(httpRequest.url));
        readStream = fs.createReadStream(filename);
        readStream.pipe(httpResponse);
    };

    fs.exists(filename, existsCallback);
 };

Does it work in-browser with HTML?

No, this is designed to run in Node.js.