vapr-output

Installation

npm install --save vapr
npm install --save vapr-output

Usage

This plugin is used to define which media types can be sent in outgoing response bodies. It performs content negotiation, ensuring that each client receives the best available media type. It also handles serialization, enabling you to use any object as a response body instead of just strings or Buffers.

const output = require('vapr-output');
const app = require('vapr')();
const route = app.get('/foo');

route.use(output({
  'application/json': body => JSON.stringify(body),
  'application/xml': body => encodeAsXML(body),
}));

route.use((req) => {
  return [[{ foo: 'bar' }]]; // Some serializable data
});

The order in which you declare each media type indicates their precedence, should the client have no preference. When a request is received without an Accept header, the first declared media type will be used.

Options

Response bodies of null or undefined will not be serialized and will not be assigned a Content-Type, because they represent "no data". For example, undefined bodies are typically used for 204 or 400 responses. However, if you want to treat null or undefined the same as any other value, you can use the encodeUndefined and/or encodeNull options.

route.use(output({
  'encodeNull': true,
  'encodeUndefined': false,
  'application/json': JSON.stringify,
}));

Media parameters are negotiated in a case-insensitive manner because many common parameters (e.g., charset) are case-insensitive. If you're using media parameters that are case-sensitive, you can reverse this behavior by setting the strictParameters option.

route.use(output({
  'strictParameters': true,
  'application/foo; some-strange-parameter=hello': serializationFunction,
}));

Sometimes you may wish to bypass content negotiation altogether. You can do this by setting the forced option.

route.use(output({
  'forced': true,
  'text/plain; charset=utf-8': String,
}));