transformer-proxy

transformer-proxy

A middleware component for node-http-proxy to transform the response from the proxied server. It can be used to transform JavaScript, pictures or any other data. If you're looking for an easy solution to modify HTML, have a look at harmon which uses trumpet for modifying HTML.

Installation

$ npm install transformer-proxy

Basic example

A basic example can be found in examples/simple.js. The quintessence is that you can tell your connect-app to use your own callback function to transform the data.

var transformerFunction = function (data, req, res) {
  // do something with the data and return it
  return data + "\n // an additional line the end of every file";
};
app.use(transformerProxy(transformerFunction));

The example also includes additional code for setting up a basic server and the corresponding proxy.

Start it as follows:

$ cd node_modules/transformer-proxy/examples
$ node simple.js

When visiting localhost:3000 you should see:

A simple HTML file

When visiting localhost:8013 you should see:

A simple HTML file
// an additional line the end of every file

Using promises

The transformation callback function may also return a promise. This is really useful for cases when the data is being transformed asynchronously (e.g. gunzipped, processed and then gzipped back). A promise-based example can be found in examples/promise.js:

var transformerFunction = function (data, req, res) {
  return new Promise(function(resolve, reject) {
    http.get('http://google.com/', function(response) {
      resolve(data + '<br />Google.com request status code: ' + response.statusCode);
    }).on('error', function(error) {
      reject(error.message);
    });
  });
};
app.use(transformerProxy(transformerFunction));

Transform only data with a certain URL

Just pass an options object as the second parameter to transformerProxy which has a match attribute. For example, if you want to modify only JavaScript files, you could use:

transformerProxy(transformerFunction, {match : /\.js([^\w]|$)/});

Transform response headers

Just pass an options object as the second parameter to transformerProxy which has a headers attribute. This attribute should be an array of objects having name and value attributes. Headers with null values will be removed. For example, if you want to modify the content type header and remove the server header, you could use:

var headers = [{
  'name' : 'content-type',
  'value' : 'application/json'
}, {
  'name' : 'server',
  'value' : null
}];

transformerProxy(transformerFunction, {headers : headers});

License

MIT © Philipp Otto