# express-mung

> Transform an express response (or make until no good)

Latest version **0.5.1** (published 2018-08-02) · MIT license · 0 weekly downloads

## Install

```sh
npm install express-mung
pnpm add express-mung
yarn add express-mung
bun add express-mung
```

## Health

**Score 23/100 (F)** — status: abandoned.

Positive: has types package; no vulnerabilities; high quality score.

Warnings: low downloads; no esm support; pre 1.0.

Negative: abandoned; low maintenance score.

## Facts

| | |
|---|---|
| Version | 0.5.1 |
| Published | 2018-08-02 |
| First published | 2015-12-08 |
| Weekly downloads | 0 |
| License | MIT |
| TypeScript types | separate (@types/express-mung) |
| Module format | CommonJS |
| Dependencies | 0 |
| Unpacked size | 30.8 KB |
| Known vulnerabilities | 0 |
| Install scripts | no |
| GitHub stars | 109 |
| Author | Richard Schneider |
| Maintainers | makaretu |
| Keywords | mung, middleware, transform, response, express |

## Links

- npm: https://www.npmjs.com/package/express-mung
- Repository: https://github.com/richardschneider/express-mung
- Homepage: https://github.com/richardschneider/express-mung#readme
- Issues: https://github.com/richardschneider/express-mung/issues
- npm.io page: https://npm.io/package/express-mung

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## Recent versions

- 0.5.1 (latest) — 2018-08-02
- 0.5.0 — 2018-04-07
- 0.4.6 — 2016-10-30
- 0.4.4 — 2016-09-13
- 0.4.2 — 2015-12-22
- 0.4.1 — 2015-12-22
- 0.3.1 — 2015-12-10
- 0.3.0 — 2015-12-09
- 0.2.0 — 2015-12-09
- 0.1.1 — 2015-12-09
- 0.1.0 — 2015-12-09
- 0.0.2-alpha — 2015-12-08
- 0.0.1-alpha — 2015-12-08

## README

# express-mung [![Build Status](https://travis-ci.org/richardschneider/express-prefer.svg)](https://travis-ci.org/richardschneider/express-mung)

Middleware for express responses.

This package allows synchronous and asynchronous transformation of an express response.  This is a similar concept to the express middleware for a request but for a response.  Note that the middleware is executed in LIFO order.  It is implemented by monkey patching (hooking) the `res.end`, `res.json`, or `res.write` methods.


## Getting started [![npm version](https://badge.fury.io/js/express-mung.svg)](https://badge.fury.io/js/express-mung)

    $ npm install express-mung --save

Then in your middleware

    var mung = require('express-mung');

    module.exports = mung.json(my_transform);

## Usage

Sample middleware (redact.js) to remove classified information.

````javascript
'use strict';
const mung = require('express-mung');

/* Remove any classified information from the response. */
function redact(body, req, res) {
    if (body.secret) body.secret = '****';
    // ...
    return body;
}

exports = mung.json(redact);
````

then add to your `app.js` file (before the route handling middleware)
````javascript
app.use(require('./redact'))
````
and [*That's all folks!*](https://www.youtube.com/watch?v=gBzJGckMYO4)

See the mocha [tests](https://github.com/richardschneider/express-mung/tree/master/test) for some more examples.

## Reference

### mung.json(fn, [options])

Transform the JSON body of the response.

`fn(json, req, res)` receives the JSON as an object, the `req` and `res`.  It returns the modified body. If `undefined` is returned (i.e. nothing) then the original JSON is assumed to be modified.  If `null` is returned, then a 204 No Content HTTP status is returned to client.

### mung.jsonAsync(fn, [options])

Asynchronously transform the JSON body of the response.

`fn(json, req, res)` receives the JSON as an object, the `req` and `res`.  It returns a promise to a modified body.  The promise returns an `object.`  If it is `null` then a 204 No Content is sent to the client.

### mung.headers(fn)

Transform the HTTP headers of the response.

`fn(req, res)` receives the `req` and `res`.  It should modify the header(s) and then return.

### mung.headersAsync(fn)

Asynchronously transform the HTTP headers of the response.

`fn(req, res)` receives the `req` and `res`.  It returns a `promise` to modify the header(s).

### mung.write(fn, [options])

`fn(chunk, encoding, req, res)` receives the string or buffer as `chunk`, its `encoding` if applicable (`null` otherwise), `req` and `res`. It returns the modified body. If `undefined` is returned (i.e. nothing) then the original unmodified chunk is used.

### Notes

* when `mung.json*` receives a scalar value then the `content-type` is switched `text-plain`.

* when `mung.json*` detects that a response has been sent, it will abort.

* sending a response while in `mung.headers*` is **undefined behaviour** and will most likely result in an error.

* when `mung.write` detects that a response has completed (i.e. if `res.end` has been called), it will abort.

* calling `res.json` or `res.send` from `mung.write` can lead to unexpected behavior since they end the response internally.

### options

- `mungError`, when `true` the munger function is always invoked.  When `false` (the default) the munger function is only invoked when the response is not in error.

## Exception handling

`mung` catches any exception (synchronous, asynchronous or Promise reject) and sends an HTTP 500 response with the exception message.  This is done by `mung.onError(err, req, res)`, feel free to redefine it to your needs.

# License
The MIT license

Copyright © 2015 Richard Schneider (makaretu@gmail.com)

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