connect-injector

A middleware to inject content into any HTTP response.


Getting Started

Install the module with: npm install connect-injector

Injecting

The basic API looks like this:

``javascript
var injector = require('connect-injector');
var middleware = injector(function when(req, res) {
// for this request and repsonse
// return whether or not to enable injecting
}, function converter(content, req, res, callback) {
content // the entire response buffer
req // the HTTP request
res // the HTTP response
callback // (error, data) with the injected data
});
`

And can be used like any other Connect and Express middleware.
You need to make sure to use the injector middleware before the actual content is being written.

Examples

$3

A very useful example for connect-injector is to add JSONP
support to any application/json repsonse:

`javascript
var injector = require('connect-injector');
var inject = injector(function(req, res) {
var isJSON = res.getHeader('content-type').indexOf('application/json') !== -1;
return isJSON && req.query.callback;
}, function(data, req, res, callback) {
callback(null, req.query.callback + '(' + data.toString() + ')');
});

// inject needs to be used before any middleware that writes to the response
connect().use(connect.query()).use(inject).use(/ your other middleware here /);
`

Now any application/json response will be wrapped into a callback if given the
callback=xyz query parameter.

$3

Another use case would be to minify JavaScript files on the fly using UglifyJS:

`js
var injector = require('connect-injector');
var connect = require('connect');
var UglifyJS = require('uglify-js');
// Cache for already uglified files
var cache = {};
// Function that uglifies JavaScript code
var uglify = function (code) {
var toplevel = UglifyJS.parse(code);

toplevel.figure_out_scope();

var compressor = UglifyJS.Compressor({
warnings: false
});
var compressed = toplevel.transform(compressor);

compressed.figure_out_scope();
compressed.compute_char_frequency();
compressed.mangle_names();

return compressed.print_to_string();
};

var inject = injector(function(req, res) {
return res.getHeader('content-type').indexOf('application/javascript') !== -1;
}, function(data, req, res, callback) {
// Check the cache, uglify the code if not and add it
if(!cache[req.url]) {
cache[req.url] = uglify(data.toString());
}

callback(null, cache[req.url]);
});

// inject needs to be used before any middleware that writes to the response
var app = connect().use(inject).use(connect.static(__dirname + '/../test'));

app.listen(8080);
`

$3

connect-injector is tested to work with http-proxy
you can rewrite existing proxied content:

`js
var httpProxy = require('http-proxy');
var connect = require('connect');
var injector = require('connect-injector');
var proxy = httpProxy.createProxyServer();
var inject = injector(function(req, res) {
return res.getHeader('content-type').indexOf('text/html') === 0;
}, function(data, req, res, callback) {
callback(null, data.toString().replace('', '

Powered by connect-injector

proxyApp.listen(8080);
`

After starting the server, check http://localhost:8080/connect-injector/dummycontent.html
to see the injected content.

Release History

__0.4.2__

- Fix for empty responses not trying to be rewritten (#13, #14)

__0.4.1__

- Fix connect-injector to work with Node 0.10.32 (#11)
- Add debug messages and remove header rewriting (#12)

__0.4.0__

- Fix issue when using GZip and refactor to use Q and proper NodeJS callbacks (#9)

__0.3.0__

- Injector works with HTTP proxy and GZipped content (#4, #7, #8)

__0.2.3__

- Fix caching issues for response headers not being written if there is no body (#3)

__0.2.2__

- Fix handling of responses with an empty body (#1)

__0.2.1__

- Fix bug not setting isIntercepted` properly

__0.2.0__

- Allow chaining injectors
- Unit tests and CI
- Fixes for writing correct headers
- Use stream-buffers instead of concatenating

__0.1.0__

- Initial alpha release

License

Copyright (c) 2016 David Luecke
Licensed under the MIT license.