req.wantsJSON
A flag indicating whether the requesting client would prefer a JSON response (as opposed to some other format, like XML or HTML.)
req.wantsJSON is used by all of the built-in custom responses in Sails.
Usage
req.wantsJSON;
Details
The intended purpose of req.wantsJSON is to provide a clean, reusable indication of whether the server should respond with JSON or send back something else. It's not the right answer for every content negotiation problem, but it is a simple, go-to solution for most use cases.
For instance, all major browsers set an "Accept: text/plain;" request header for requests typed in the URL field. In this case, req.wantsJSON is false. For many other cases, though, the distinction is less clear. In those scenarios, Sails uses heuristics to determine the best value for req.wantsJSON.
Technically, req.wantsJSON inspects the request's "Content-type", "Accepts", and "X-Requested-With" headers to determine whether the request expects a JSON response. If the information in these headers is too scanty, Sails errs on the side of JSON, and req.wantsJSON will be set to true.
The benefit of req.wantsJSON is that it future-proofs your app and makes it less brittle. As best practices for content negotiation change over time (e.g. a new type of consumer device or enterprise user agent introduces a new header), Sails can patch req.wantsJSON at the framework level and modify the heuristics accordingly. It also reduces code duplication and saves you the annoyance of manually inspecting the headers in each of your routes.
Example
if (req.wantsJSON) {
sails.log('This request wants JSON!');
}
else {
// `req.wantsJSON` is falsy (undefined), to this request must not want JSON.
}
Details
Here is the specific order in which req.wantsJSON inspects the request. If any of the following match, subsequent checks are ignored.
A request "wantsJSON" if:
- it looks like an AJAX request
- it's a virtual request from a socket
- the request DOESN'T explicitly want HTML
- the request has a "json" content type AND has its "Accept" header set
req.options.wantsJSONis truthy
Notes
- Lower-level content negotiation is, of course, still possible using
req.is(),req.accepts(),req.xhr, andreq.get().- As of Sails v0.10, requests originating from a WebSocket client always want JSON.
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Reference
- Application
- Blueprint API
- Command-line interface
-
Configuration
- sails.config.*
- sails.config.blueprints
- sails.config.bootstrap()
- sails.config.custom
- sails.config.datastores
- sails.config.globals
- sails.config.http
- sails.config.i18n
- sails.config.log
- sails.config.models
- sails.config.policies
- sails.config.routes
- sails.config.security
- sails.config.session
- sails.config.sockets
- sails.config.views
-
Request (`req`)
- req._startTime
- req.body
- req.cookies
- req.fresh
- req.headers
- req.hostname
- req.ip
- req.ips
- req.isSocket
- req.method
- req.options
- req.originalUrl
- req.params
- req.path
- req.protocol
- req.query
- req.secure
- req.signedCookies
- req.socket
- req.subdomains
- req.url
- req.wantsJSON
- req.xhr
- req.accepts()
- req.acceptsCharsets()
- req.acceptsLanguages()
- req.allParams()
- req.file()
- req.get()
- req.is()
- req.param()
- req.setLocale()
- req.setTimeout()
- req.host
- Response (`res`)
- Waterline (ORM)
- WebSockets
Reference
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