A declarative way to set HTTP headers from react components.

NOTE: this project is very much under construction, you should NOT use it in production just yet.

Because this thing isn't finished yet, I've not put it on npm yet. For now, you can install it using:

npm install --save romeovs/react-headers

// in a component
import React   from 'react'
import Headers from 'react-headers'

class Foo extends React.Component {

  render () {
    // ...
    return (
      <div>
        // ...
        <Headers
          cacheControl = 'public; max-age=60'
          // could also be:
          // cacheControl = {{ public: true,  'max-age': 60   }}
          // CacheControl = {{ public: true,  maxAge: '1m' }}
        />
      </div>
    )
  }
}

When rendering on the server you can then do:

ReactDOM.renderToString(<Foo/>)
const headers = Headers.rewind()
// { 'Cache-Control': 'public; max-age=60' }

You can then set these headers using express or koa.

Setting the headers for a simple html page is simple enought using just react and express or koa. It becomes complicated however if you have multiple components on the page that have their own concerns and need to set their own headers.

For instance, consider a component A, that shows some data that should be cached publicly with a max-age of 1w. Meanwhile component B, which might or might not be shown together on the page with component A, contains data that will turn stale after only 1d. It might be hard to figure out how to reconcile these concerns, and to decide when to set which max-age. Using react-headers this is no longer a problem, because it merges the headers of all active components on the page in a logical way. In our example, a page with both A and B on it (containing data that goes stale afer 1w and data that goes stale after 1d), should go stale after 1d, so react-headers merges the headers to reflect this.

A -> Cache-Control: public; max-age=1w  --+
                                          | --> A + B -> Cache-Control: public; max-age=1d
B -> Cache-Control: public; max-age=1d  --+

react-headers has merging algorithms for the headers where it makes sense.

On top of that, react-headers provides some niceties such as a nice expiry format (1m, 1d, ...) for timeouts and dates and simple interpolations of header formats.

1. Implement parsing and merging algorithms for all response headers where it makes sense to have them in react-headers - [ ] Acces-Control-Allow-Origin - [ ] Age - [x] Allow - [x] Cache-Control - [ ] Content-Disposition - [ ] Content-Description - [ ] Content-Language - [ ] Date - [x] Expires - [x] Last-Modified - [x] Link - [ ] Refresh - [ ] Retry-After - [ ] Set-Cookie (?) - [x] Status - [ ] Warning - [ ] WWW-Authenticate (?)

2. make sure the client-side included code is as small as possible