get header size and file size (compressed, uncompressed) of node HTTP requests (with gzip, deflate, or no compression)

httpSizes.js

var http = require('http');
var request = require('request');

var zlib = require('zlib');


var opts = {
  method: 'GET',
  url: '<url>',
  // headers: {'Accept-Encoding': 'gzip, deflate'}
};

var req = request(opts).on('response', function(res) {
    // Raw headers were added in v0.12 (https://github.com/joyent/node/issues/4844),
    // but let's reconstruct them.
    var rawHeaders = ('HTTP/' + res.httpVersion + ' ' + res.statusCode +
                      ' ' + http.STATUS_CODES[res.statusCode] + '\r\n');
    Object.keys(res.headers).forEach(function(headerKey) {
        rawHeaders += headerKey + ': ' + res.headers[headerKey] + '\r\n';
    });
    rawHeaders += '\r\n';

    console.log(res.headers['content-encoding']);

    switch (res.headers['content-encoding']) {
        case 'gzip':
            var gzip = zlib.createGunzip();

            var uncompressedSize = 0;  // size after uncompression
            var bodySize = 0;  // bytes size over the wire

            gzip.on('data', function (data) {
                uncompressedSize += data.length;
            }).on('end', function () {
                console.log('headersSize:', Buffer.byteLength(rawHeaders, 'utf8'));
                console.log('content.size uncompressed:', uncompressedSize);
                console.log('bodySize compressed:', bodySize);
                console.log('compression:', uncompressedSize - bodySize);
            });

            res.on('data', function (data) {
                bodySize += data.length;
            }).pipe(gzip);

            break;
        case 'deflate':
            var deflate = zlib.createInflate();

            var uncompressedSize = 0;  // size after uncompression
            var bodySize = 0;  // bytes size over the wire

            deflate.on('data', function (data) {
                uncompressedSize += data.length;
            }).on('end', function () {
                console.log('headersSize:', Buffer.byteLength(rawHeaders, 'utf8'));
                console.log('content.size uncompressed:', uncompressedSize);
                console.log('bodySize compressed:', bodySize);
                console.log('compression:', uncompressedSize - bodySize);
            });

            res.on('data', function (data) {
                bodySize += data.length;
            }).pipe(deflate);

            break;
        default:
            var uncompressedSize = 0;  // size after uncompression
            var bodySize = 0;  // bytes size over the wire

            res.on('data', function (data) {
                uncompressedSize += bodySize += data.length;
            }).on('end', function () {
                console.log('headersSize:', Buffer.byteLength(rawHeaders, 'utf8'));
                console.log('content.size uncompressed:', uncompressedSize);
                console.log('bodySize compressed:', bodySize);
                console.log('compression:', uncompressedSize - bodySize);
            });

            break;
    }
});

Still very handy! Thanks for this 4 year old script ;-)

For uncompressed requests you have "uncompressedSize += bodySize += data.length" to calculate compressed/uncompressed sizes. Is that correct?