I'm writing some rest API with Node.JS and Express. So for each API, I'd need to do all the usual stuff like parameter validation, authentication, authorization and then the actual business logic. Some sodo code to illustrate this:
router.get('/users', function (req, res){
async.auto(
authenticateCaller();
authorizeCaller();
validateParams();
doGetUsers();
)
})
This style certainly works but it makes the whole function very cumbersome by including a lot of extra pre-purpose codes. I know in web app programming, MVC has been introduced to separate UI, Module and Controller into different code groups, which is much cleaner. Is there any similar framework that can be helped to achieve this purpose?
Use middleware. Middleware is just a function that takes in three parameters:
function (req, res, next) {}
Call router.use() to register middleware before defining any routes. This will cause that middleware to be called before every route is executed.
These are all functions of middleware:
authenticateCaller();
authorizeCaller();
validateParams();
http://expressjs.com/en/guide/using-middleware.html
This is what I do.
Using Routes for Node.js Here I am making way for a folder named routes that has all the codes in it.
var routes = require('./routes');
var route_add_user = require('./routes/add_user');
Calling the function with the route here; .adduser is function name within that js file
app.get('/adduser', route_add_user.adduser);
define a function do your routine jobs
fuction auth(res,req,next){
authenticateCaller();
req.isAuthorized = authorizeCaller();
validateParams();
next();
}
router.get('/users',auth);
router.get('/users', function (req, res){
if( req.isAuthorized)
{..do some stuff here..}
})
This is one of the STYLE i was following to authenticate and use the API in express framework.
register.js
-----------
exports.addUser = function(req, res) {
// do something
};
exports.deleteUser = function(req, res) {
// do something
};
routes.js
---------
var register = require('./register');
router.get(‘/register’,auth, register.addUser);
router.get(‘/deleteUser’,auth, register.deleteUser);
// Better make it separate common file to reuse all the API
function auth(req,res,next) {
// do something to authenticate your API
}
Related
I could not find the official docs in a google search. Where are the official API docs for express.Router() and are lines 1 and 2 the same?
If so, is it just a matter of preference on which to use?
const express = require('express');
const router = express.Router();
router.get('path', callback); // line 1
router.route('path').get(callback); // line 2
There are 3 ways with which you can declare routes in your application
These are:
app.get("path", fn)
router.get("path", fn)
router.route("path").get(fn)
All of the above functions are used to generate http request routes in your application.
The app.get is the most basic one and is not recommended for larger projects. The reason being it gives less flexibility in handling routes as compared to the express.router. In express applications you will be dealing with middlewares a lot. Middlewares are functions that are executed before the controller function of your application
For example, take a look at this line
app.get("/user", verifyUser, createUser);`
Above, verifyUser is a middleware function that is called with (Request, Response, Next) arguments by the express framework, you can write your incoming request verification logic in verifyUser and can then callNextFunctionto pass the control to the next function with is thecreateUsercontroller;
You can have as many middlewares as you want in your route declaration.
What if you need to call verifyUser each time a user is created, removed, fetched or modified. For each of the actions, you need to define your routes like this:
app.get("/user", verifyUser, fetchUser);
app.put("/user", verifyUser, updateUser);
app.post("/user", verifyUser, createUser);
app.delete("/user", verifyUser, deleteUser);
In larger applications you need to defined different logics to different entities and routes.
express.router solves the above problem by providing us a flexibility to define what to do when user lands the /user route before passing the request to the middleware.
The above code in express router can be written as follows:
// file: userRoutes.js
const router = express.Router();
router.use((req, res, next) => {
verifyUser(req, res, next);
});
function verifyUser(req, res, next) {
// verification logic here
if (/** verification is successful */)
return next(); // return to the controller
res.status(400).json({ msg: "user does not exists" });
}
router.get("/user", fetchUser);
router.put("/user", updateUser);
router.post("/user", createUser);
router.delete("/user", deleteUser);
module.exports = router;
// app.js
const userRoutes = require("./userRoutes");
app.use(userRoutes);
Things gets really simplified if we chain the http request methods in the following way:
router.route("/user")
.get(fetchUser);
.put(updateUser);
.post(createUser);
.delete(deleteUser);
Note: Above code is for explanation purpose only, there may be syntax errors, the code is not expected to run as it is. User might need to alter the code to make it work.
Is it possible to create a function somewhere that can be called from any view in my express js mvc web app? How to declare such function in middleware to be accessed directly from a view?
So I can call this function like:
<%= getVar('my_name') %> // calling from the view
and implement return logic of the variable where the function is declared. This function may use request and response objects.
Note: 'my_name' can be anything on the view which cannot be assigned from the controller.
You can add functions to app.locals or res.locals just like you would add variables to it. If you want to have the request and response available in there (which, frankly, I feel bleeds a bit into what your controllers should be doing), you could create a middleware and pass those in.
From what you said in your comment, it's actually best to just set the variable that the view can use, eg:
app.use((req, res, next) => {
res.locals.value = req.session.value || 'default value';
next();
});
if you really need the function to be usable in the view, you can set it the same way, and bind the request and response to the function if needed:
function getVar(req, res, anotherArg) {
// do whatever
}
app.use((req, res, next) => {
res.locals.getVar= getVar.bind(null, req, res);
next();
});
How do you access application configuration settings inside a middleware function with express? For example say I have the following contrived example which is defined it's own module and I want to branch based on the results of a application configuration.
function fail(req, res, next) {
if (app.config.fail === true) {
res.json({'err': 'failed'});
}
return next();
}
What is correct way to handle this with express?
Well, if you wanna access app inside a middleware you can do that with req.app. As explained here
I hope this is what you were looking for!
I'm just getting started with express.js and am failing to understand how one defines discrete "pages" (in the traditional sense) that one can link to internally.
I'm using Jade as a template engine and I see how it pulls the various components together and references them in the app.js (which is what is initially invoked by npm) so that, in effect is my "index". Would be great to see a tutorial on what one does to then build out pageA, pageB, pageC so that they can be linked to via <a href="pageA.html"> (or the Jade equivalent).
I'm assuming this is possible, right?
Express.js itself does not offer URL generation, only a built-in router.
You would need to use an additional package to perform URL generation, or build it yourself. Maybe you find something fitting in this question's answers: URL generation for routes in express
If you do not care about route generation and want to "hard code" the URLs, you would need to add a route for each static page, like this:
// routes.js
app.get("/pageA.html", function(req, res, next) { res.render("static/page_a", { templateLocals: "here" }) };
app.get("/pageB.html", function(req, res, next) { res.render("static/page_b") };
Or, if you have many of those pages, you could use a controller for this:
// static_page_controller.js
module.exports = function(pageTemplate) {
return function(req, res, next) {
return res.render("static/" + pageTemplate);
}
}
And use it like this:
// routes.js
var staticController = require("./static_page_controller");
app.get("/pageA.html", staticController("page_a"));
I'm using nodejs with the mojito mvc framework.
Do I have access to some global variables from middleware? How can I use Y.mojito.models in middleware?
// ./middleware/mymiddleware.js
module.exports = function (req, res, next) {
// How to use Y?
//Y.log('fails');
//Y.mojito.models['MyModel'].fetch(function(err, data) {
// next();
//});
};
I strongly recommend not to try to do that. Those are express middleware, they are suppose to do a quick job, sometimes async job but generally, if the request is meant to be processed by mojito dispatcher engine, you should not try to access runtime components in a middleware.
That been said, there is an internal API (that again I strongly recommend not to use) that will give you access to the global Y which holds all the YUI modules at the server side. Something like this:
module.exports = function (config) {
// then `config.Y.mojito.models['MyModel'].fetch()` is available here
return function (req, res, next) {
next();
}
};
Aside from that, if what you're looking for is a way to share models, or expose global models, you should look at mojito-models-addon, expose method.
Again, the config.Y thing is private and we might change that at any time.
update: in mojito there are two types of middleware, the traditional express middleware and the mojito middleware, which will have to be prefixed with mojito-, and these are the one that should expose a function that receives config and returns a transitional express middleware. Without the prefix, it will just be called per requests without preparation.