GCFrame

Help serve HTTP endpoints with Google Cloud Functions.

Cors

The CORS middleware helps allow/deny access to an HTTP function based on CORS request headers. If it does not receive an Origin header it will allow access.

$3

``
npm install -s gcframe-cors
`

$3

`
cors(options, [, next])
`

Allows/denies HTTP access to a function based on CORS request headers received.

| Argument | Desription | Default |
| ----------| -------------------------------------------------------------------|----------|
| options.allowOrigin | An Array object containing a list of allowed origins. Or a special case * string to match all origins. | [] |
| options.allowMethods | An Array object containing a list of allowed methods. | ['GET'] |
| options.allowHeaders | An Array object containing a list of allowed headers. | [] |
| next | A gcframe/middleware function, or the cloud function itself. If not provided the function returns a "partially applied" function which will except the next argument. | required |

The cors function will add appropriate CORS headers to a response to allow or deny the browser from accessing the response.

Access-Control-Allow-Origin will be set with the value of the Origin header of the request if...
* it is included in options.allowOrigin list, or
the special case is used in options.allowOrigin.

Access-Control-Allow-Headers will be set with any headers included in options.allowHeaders list.

Access-Control-Allow-Methods will be set with any methods included in options.allowMethods if the request method was OPTIONS.

Read more about CORS on the MDN web docs.

$3

`
const cors = require('gcframe-cors');

// Define google cloud function, main handler.
function helloWorld (req, res) {
return res.send(Hello world);
}

// Allow all origins to make POST requests to the function.
var functionWithCors = cors({ allowOrigin: '*', allowMethods: 'POST' }, helloWorld)

module.exports = {
helloWorld: functionWithCors,
}
`

#### Compose router with other gcframe functions

gcframe functions are auto-curried handler-last functions, so they can be composed in a functional style.

`
const router = require('gcframe-router');
const cors = require('gcframe-cors);

// Define google cloud function, main handler.
function helloWorld (req, res) {
// Access named parameter key.
return res.send(Hello ${req.params.name});
}

// Match GET requests with a single named parameter.
const routerMiddleware = router('GET', '/:key');
// Allow all origins to make POST requests to the function.
const corsMiddleware = cors({ allowOrigin: '*', allowMethods: 'POST' }, helloWorld)

// Compose gcframe functions into a single middleware function.
const handle = compose(corsMiddleware, routerMiddleware);

module.exports = {
helloWorld: handle(helloWorld),
}
```