I'm pretty new to node.js and express and I was wondering if there's a way to define a route that calls upon another route simply to collect data and not to completely reroute.
I've got a route set up as follows:
app.get("/databases/list", function(req, res) {
db.listDatabases().then(names => {
res.send(names);
});
});
Subsequently I'd like to have a different route, say:
app.get('/whatever', function(req, res) {
// here I'd like to make a call to retrieve the information from the first route
// then I'd like to do something with that information, I want to stay in the same route.
}
Is this possible?
Expanding #marcobiedermann answer, In your case simply make a controller and and use the FUNCTION in both the routes. You don't need to fetch anything.
/// --- Controller ----
class SimpleController {
constructor(db){
this.db = db;
}
listDatabase(/*maybe optional callback*/){
return this.db.listDatabases();//or something....
}
whatever(/*maybe optional callback*/){
return this.listDatabase()
.then(process)
}
}
/// --- Routes ----
const sController = new SimpleController(db);
app.get("/databases/list", function(req, res) {
sController.ListDatabase().then(names => {
res.send(names);
});
});
app.get('/whatever', function(req, res) {
sController.whatever()
.then(....)
}
Yes this is possible.
You have to fetch the data from your first endpoint.
fetch('/databases/list')
.then( … )
This requires the /databases/list route to be defined before your /whatever route.
However, I would strongly advice you to NOT do this.
You should abstract your logic into a controller and call this controller in both of your routes:
const fetchController = {
fetchData: () => {
return fetch('path/to/data/to/fetch')
.then( … )
// or database call or wherever you might get the data from
}
}
app.get('/databases/list', (req, res) => fetchController.fetchData());
app.get('/whatever', (req, res) => fetchController.fetchData());
app.get("/databases/list", async function(req, res) {
return await db.listDatabases();
});
app.get('/whatever', async function(req, res) {
const result = await fetch('path/databases/list');
console.log(result)
});
It might help you, But it's not recommended way. You can create method (common somewhere in the controller) and use that where ever you need.
Related
I'm trying to figure out a way to use req.params as an argument in my middleware. Take this (obviously broken) code for example:
router.post('/:myParam', checkSchema(schemas[req.params.myParam]), async (req, res, next) => {
// do stuff
})
The goal here is that I am using express-validator and I load a dynamic schema based on what param is passed. The above code is obviously broken because I don't yet have the scope to access the req variable, I'm just trying to illustrate what I'm trying to accomplish.
if you know the possible params ahead, you could do something like the following:
router.post("/:myParam", checkSchema("soccer"), async (req, res, next) => {});
//checkSchema.JS
const soccerSchema = require("../schemas/soccerSchema");
const swimmingSchema = require("../schemas/swimmingSchema");
module.exports = function (schemaName) {
return (req, res, next) => {
const schemas = { soccer: soccerSchema, swimming: swimmingSchema };
//You can access it here schemas[schemaName]
console.log(schemas[schemaName]);
next();
};
};
You can directly call schemas(req.params.myParam) inside the checkSchema middleware since the middleware will have access to the request object.
I know that I can chain middleware functions after passing in the route like
const express = require('express');
const router = express.Router();
router.post('/', middlewareFunction1, middlewareFunction2, controllerFunction);
module.exports = router;
I would like to know if it's possible to call only one function (called gateway)
router.post('/', gatewayFunction1);
and this function is able to chain all those methods
const controller = require('../controllers/controller');
function gatewayFunction1(request, response, next) {
// validate route
// do other middleware stuff
// call controller.function1
}
module.exports = {
gatewayFunction1,
};
Why would I do that? I was thinking about separating the middleware logic from the routes. This gateway should just get executed after routing and before calling the router.
I tried to return an array of functions (example code)
function gatewayFunction1(request, response, next) {
return [(request, response, next) => {
console.log('called middleware 1');
next();
}, (request, response, next) => {
console.log('called middleware 2');
next();
}, (request, response, next) => {
response.status(200).json({
message: 'that worked',
});
}];
}
but when I call this api route I get no response
Could not get any response
so it keeps loading forever. Is there a way to chain these middleware functions within another function?
Your gatewayFunction1 does nothing except returns an array.
Just use router.
const express = require('express');
const gatewayFunction1 = express.Router();
gatewayFunction1.use(middlewareFunction1, middlewareFunction2, controllerFunction);
module.exports = gatewayFunction1;
Then
const gatewayFunction1 = require('...'); // where you define gatewayFunction1
router.post('/', gatewayFunction1);
Middleware should be a function and you are returning an array.If next function is not called it will get stuck. I don't like the whole idea combining them but I think the best way is to import all your middleware functions in one function and call them individually then use that function as your combined middleware.
I have the following router.use calls in one of my routers
router.use("/:collection/", (req) => {
return require(`./${req.params.collection}`);
});
and that calls in this example, example.js
example.js is as follows:
const header = require("../../header"); //gets our header that declares everything
const router = header.express.Router(); //makes our router for collections requests
console.log("123");
///The Following is when a name is requested
router.get("/test", (req, res, next) => {
console.log("test");
res.json({msg:"hi"});
next();
});
module.exports = router; //makes our router avialable
you'd expect when:
http://localhost:3000/api/example/test
is request that it would write in the console something to the effect of:
123
test
and I would get the response:
{msg:"hi"}
Instead the console gets just:
123
written and there is no response.
It seems the
router.get
in the example.js is never called, can someone tell me why?
I fixed it, instead of
router.use("/:collection/", (req) => {
return require(`./${req.params.collection}`);
});
I use
router.get("/:collection", (req, res) => {
//this is my other call that will do stuff in the parent file
//we don't call next because it is already matched, otherwise we call next
});
router.use("/:collection/", (req, res, next) =>{ //says if it gets here pass on the info
router.use("/:collection/", require(`./${req.params.collection}`)); //then route
next();
});
I want to use routes something like this.
For example :
routes.use((req, res, next) => {
/**
* I have an example routes from database and i was passing into variable
* I'm assign fromDb as 'api/test'
*/
var a = fromDb;
next()
})
routes.get(a, (req, res, next) => {
console.log(req.path)
})
I know, a variable in next routes do not get a value from DB cause functional scope. So, any idea for solve this method. I just wondering if I can using modular like this
const DBRoutes = require('lib/example.js')
router.get(DBRoutes, (req, res) => {
console.log(req.path)
})
Any idea for the best method? Thanks
You want to add a route based on content in your database
So you could do the lookup and on success create the route
eg:
dbConnection.lookup(...some query)
.then((pathFromDB) => {
// where pathfromDb = /api/test
routes.get(pathFromDB, (req, res, next) => {
console.log(req.path)
})
});
routes.use((req, res, next) => {
/**
* I have an example routes from database and i was passing into variable
* I'm assign fromDb as 'api/test'
*/
res.locals.fromDb = fromDb;
next()
})
routes.get('/your/route', (req, res, next) => {
console.log(req.path);
console.log(res.locals.fromDb);
});
This is one way of passing variables through different middlewares in express.
I don't think you can dynamically set up routes for express web server. However, routes are set up once during startup. You can get the routes from database at that time.
const route = await routeFromDatabase();
routes.get(route, (req, res, next) => {
console.log(req.path);
console.log(res.locals.fromDb);
});
If you change the database after startup, you will have to restart the node app.
Update 19th Feb 2018: User mentioned the use case as API Gateway. This is worth exploring for such use cases: https://www.express-gateway.io/
I'm working in a restful service using express.js and i want to enhance the req and res variables so for example you could write something like
app.use(function (req, res, next) {
res.Ok = function (data) {
res.status(200).send(data);
};
res.InternalError = function (err) {
res.status(500).send(err);
};
});
And later
router.get('/foo', function (req, res) {
res.Ok('foo');
})
This will send 'foo' in the body of the response and set the status code to 200 and is working perfectly.
My first question is if it is possible to add such functionality without a middleware function, lets say in a property or the prototype of the app variable?
The second question is if there are performance issues if you add many functionality with middleware functions at the app level. Are this functions attached to the request and response object per request or once on the application startup?
I know the Sails framework already do this but I'm wondering if they use middleware functions as well.
I keep digging and turns out that the request and response object are exposed in express using the __proto__ property.
var express = require('express'),
app = express();
app.response.__proto__.foo = function (data) {
this.status(200).send(data);
};
And later in the router
router.get('/foo', function (req, res, next) {
res.foo('test');
});
This will print test in your browser so it is possible to add functionality without using any middleware.
Note: I'm sure there are some drawbacks to this approach (overwriting express predefined properties, for example) but for testing purposes and adding very simple functionality I think is slightly better in terms of performance.
I'm not aware of any other way than using middleware. But in my opinion you could do the following to achieve nearly the same thing.
// Some Route
router.get('/foo', function(req, res, next) {
// ...
if(err) {
res.status(500);
return next(err);
}
return res.send('ok');
});
// Another route
router.get('/bar', function(req, res, next) {
// ...
if(badUserId) {
res.status(400);
return next('Invalid userId.');
}
req.result = 'hello';
return next();
});
router.use(function(req, res) {
// I prefer to send the result in the route but an
// approach like this could work
return res.send(req.result);
});
// Error Middleware
router.use(function(err, req, res, next) {
if(res.statusCode === 500) {
// Log the error here
return res.send('Internal server error');
} else {
return res.send(err);
}
});