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\n\nExpress-interceptor allows you to define a previous step before sending a response. This allows you to do anything you want with the response, such as processing, transforming, replacing, or logging it. Express-interceptor allows you to avoid calling `next()` over and over. Further more, you can avoid managing nested scopes. Using a declarative API, it’s simple to use and maintain.\n\nSome use cases include:\n\n- Transpile custom elements into standard HTML elements.\n- Transform JSX or compile less files on the fly.\n- Store statistics about responses.\n- Set response headers based on tags in the response body.\n- Dynamically inject live-reload scripts to HTML.\n\n## Usage\n\nInstall the package\n\n\n npm i --save express-interceptor\n\nDefine your interceptor\n\n```javascript\nvar express = require('express');\nvar cheerio = require('cheerio');\nvar interceptor = require('express-interceptor');\n\nvar app = express();\n\nvar finalParagraphInterceptor = interceptor(function(req, res){\n return {\n // Only HTML responses will be intercepted\n isInterceptable: function(){\n return /text\\/html/.test(res.get('Content-Type'));\n },\n // Appends a paragraph at the end of the response body\n intercept: function(body, send) {\n var $document = cheerio.load(body);\n $document('body').append('From interceptor!
');\n\n send($document.html());\n }\n };\n})\n\n// Add the interceptor middleware\napp.use(finalParagraphInterceptor);\n\napp.use(express.static(__dirname + '/public/'));\n\napp.listen(3000);\n\n```\n\nYou're defining an interceptor that will be executed whenever the response contains html as Content-Type. If this is true, it will append a child at the end of the body. In other words, it will transform the response:\n\n```html\n\n\n\n\"Hello world\"
\n\n\n```\n\nInto:\n\n```html\n\n\n\n\"Hello world\"
\nFrom interceptor!
\n\n\n```\n\nSee [more examples](https://github.com/axiomzen/express-interceptor/tree/master/examples). Also, you can debug express-interceptor actions using [debug](https://github.com/visionmedia/debug) env variable `DEBUG=express-interceptor`.\n\n## API\n\n* `isInterceptable()` (required): is a predicate function where you define a condition whether or not to intercept a response. Returning `true` buffers the request, and proceeds calling `intercept()` as well as `afterSend()`. Typically, you want to check for this condition in the `res` object in the definition of the middleware.\n\n* `intercept(body, send)` (required): Parse the body as an encoded string. After processing the body, call `send(newBody)` with the content to be sent back to the client.\n\n* `afterSend(oldBody, newBody)`: This method will be called after sending the response to the client – after the `done()` callback in the `send()` method is executed. This method would typically be used to cache something, log stats, fire a job, among other things.\n\n## Who is using it?\n\n* [node-stylus-require](https://www.npmjs.com/package/node-stylus-require)\n* [express-html-minify](https://www.npmjs.com/package/express-html-minify)\n* [express-jare](https://www.npmjs.com/package/express-jare)\n* [hospitalrun-server-routes](https://www.npmjs.com/package/hospitalrun-server-routes)\n\n## Similar to\n\n- [express-hijackresponse](https://github.com/papandreou/express-hijackresponse)\nDifferent API, using callbacks with no top down structure, more obtrusive to HTTP internals.\n\n- [hijackresponse](https://github.com/gustavnikolaj/hijackresponse)\nAttempting to solve same problems than `express-hijackresponse`. Different API using pipes, recommended if you have problems with [streaming](https://github.com/axiomzen/express-interceptor/issues/15) or if you need more control over responses.\n\n- [tamper](https://github.com/fgnass/tamper)\nSimilar functionality but different internals and API.\n\n## Words of advice\n\nIf your `intercept` method make calls to a database, or needs to make expensive transformations to the original response, you should take in account the time that will add to the response. You should define your `isInterceptable` method carefully, checking the type of the response, or even the route that was fired by the request, also you may consider implementing a cache strategy to get faster responses.\n\nIf you face any issue, don't hesitate to submit it [here](https://github.com/axiomzen/express-interceptor/issues).\n\n## Contributing\n\nPlease check [CONTRIBUTING.md](CONTRIBUTING.md).\n\nThis project adheres to the [Open Code of Conduct](http://todogroup.org/opencodeofconduct/#express-interceptor/ipinoraul@gmail.com). By participating, you are expected to honor this code.\n\n## Author\n\n* [AxiomZen](https://www.axiomzen.co/).\n\n## Collaborators\n\n* [Fabiano Soriani](https://github.com/flockonus).\n* [Raul Pino](https://github.com/p1nox).\n\n## License\n\n [MIT](LICENSE)\n","maintainers":[{"name":"flockonus","email":"fabianosoriani@gmail.com"},{"name":"p1nox","email":"ipinoraul@gmail.com"}],"time":{"modified":"2022-06-17T22:21:38.493Z","created":"2015-03-06T21:08:16.690Z","0.1.0":"2015-03-06T21:08:16.690Z","1.0.0":"2015-03-16T20:10:37.402Z","1.0.1":"2015-05-25T19:16:31.673Z","1.1.0":"2015-08-05T13:19:55.479Z","1.1.1":"2015-08-05T14:02:56.833Z","1.2.0":"2016-04-03T14:34:24.787Z"},"keywords":["express","expressjs","middleware","modify","response","hack","interceptor","hijack","hijackresponse"],"contributors":[{"name":"Fabiano P Soriani","email":"fabianosoriani@gmail.com","url":"https://github.com/flockonus"},{"name":"Raul Pino","email":"ipinoraul@gmail.com","url":"https://github.com/p1nox"}],"author":{"name":"AxiomZen","url":"https://axiomzen.co"},"license":"MIT","readmeFilename":"README.md","users":{"flockonus":true,"rankun203":true,"benjaminokeefe":true,"dburdese":true,"goliatone":true,"shakakira":true,"zeke":true,"tonillo":true},"homepage":"https://github.com/axiomzen/express-interceptor#readme","repository":{"type":"git","url":"git+https://github.com/axiomzen/express-interceptor.git"},"bugs":{"url":"https://github.com/axiomzen/express-interceptor/issues"}}