Handling Errors & Improving the Project Setup | Creating a REST API with Node.js

00:00:01 welcome back to the serious over the
00:00:04 last videos we already worked quite a
00:00:06 bit on our restful api and I liked how
00:00:10 it looked said works really great now we
00:00:14 added some routes and zhan it's now time
00:00:16 to improve our development set up a
00:00:18 little bit at least and I always want to
00:00:20 make sure that we improve error handling
00:00:23 because we're not really handling errors
00:00:25 in our API as of now
00:00:31 so first of all what I want to improve
00:00:34 regarding the setup is I don't
00:00:36 constantly want to restart the server
00:00:39 whenever we make a change to anything
00:00:41 for this we can use a package called
00:00:43 node Mon we install it with the NPM
00:00:46 install and then – – save def because 3
00:00:49 is only a development dependency we need
00:00:51 and then the name is just node Mon just
00:00:53 download it like this this is a package
00:00:56 which will basically monitor your files
00:00:58 and automatically restart the server
00:01:00 whenever you change something a link to
00:01:03 the package can be found in the video
00:01:05 description and there you can learn more
00:01:07 about it so now with that note one was
00:01:10 added I now also want you no longer
00:01:14 manually type note server but instead
00:01:17 with node Mon we would have to type node
00:01:20 Mon server je s that however will fail
00:01:23 because it's not a global package
00:01:25 installed on our machine now we can
00:01:29 easily work around this by going to the
00:01:31 package.json file and adding a script
00:01:34 let's add the start script that's a
00:01:37 special script we can easily execute by
00:01:40 running NPM start inside our project
00:01:42 folder and when we type this I want to
00:01:45 run node 1 here I can use that because
00:01:49 this will now not search for it on our
00:01:51 cert system but in our project and there
00:01:54 we just installed it so then I want to
00:01:56 execute node 1 server je s now if I run
00:02:00 NPM start here you see we got this
00:02:03 output here looks a little bit different
00:02:05 than before and it essentially started
00:02:07 our server so if I go back to postman
00:02:11 and I try my requests again this still
00:02:14 works because we got a no js' server but
00:02:17 watch the console if I added something
00:02:20 so here I'll simply add a comment routes
00:02:25 which should handle requests and now if
00:02:28 I save this file
00:02:30 you see it's restarting the server even
00:02:33 though here I didn't add any logic that
00:02:35 would have required that but it watched
00:02:36 the file and saw that I changed it and
00:02:39 this all the works for files and
00:02:41 subdirectories here if I say handle
00:02:44 incoming get requests to slash orders
00:02:48 and I save this
00:02:50 it also restarted so this is really
00:02:53 convenient now we don't have to manually
00:02:55 cancel the server and restart whatever
00:02:57 make a change
00:02:59 additionally I want to add a logging
00:03:01 package to my set up to log incoming
00:03:05 requests so that we can also see some
00:03:07 information here in the terminal so for
00:03:10 that I'll temporarily quit node Mon and
00:03:13 install another package with NPM install
00:03:16 – – save and it's called Morgan
00:03:19 it's a logging package for node J s we
00:03:22 can use it really easy just go to app J
00:03:26 s and there let's create a new constant
00:03:29 its name at Morgan and require the name
00:03:33 is by the way totally up to you
00:03:34 require Morgan this name is not up to
00:03:36 you that has to be the package you
00:03:37 installed and now we have to basically
00:03:40 tell Express to funnel all requests
00:03:43 through this middleware that it is in
00:03:46 the end and Morgan will then just log
00:03:48 something and let the request continue
00:03:50 so Morgan behind the scenes will call
00:03:53 this next function saying I don't return
00:03:56 a response I just did something in this
00:03:59 case I locked something you continue
00:04:01 doing your work so let's use Morgan and
00:04:05 let's use it before we handle our
00:04:08 requests with our routes by simply
00:04:10 saying app use and then use some more
00:04:13 again as a function and pass death here
00:04:17 that's the format we want to use for the
00:04:19 output now with that let's rerun NPM
00:04:23 start to restart node Mon and if I now
00:04:27 again send a request here it looked as
00:04:29 before but you see now in a terminal we
00:04:32 get this extra log seeing that we got a

00:04:34 get request and how long it took and so
00:04:37 on so that's really nice additionally I
00:04:40 now want to handle errors keep in mind
00:04:43 if we send a request to some invalid ID
00:04:46 or with some invalid HTTP word we get
00:04:49 back this default error HTML page and I
00:04:52 want to send back JSON instead now error
00:04:55 handling is really nice in
00:04:58 set up here keep in mind that we have
00:05:00 here our middleware which forwards
00:05:02 requests to products and orders files
00:05:06 where we then have to router on the
00:05:08 apprehend that means if we make it past
00:05:11 these two middlewares
00:05:13 none of the routes set up an IVA of the
00:05:16 two files were suited to handle the
00:05:18 incoming requests hence we can handle
00:05:21 errors by simply catching all requests
00:05:24 that make it past these two requests
00:05:26 here these two middlewares I should say
00:05:28 so we can something use the app object
00:05:31 and now use and no longer add a filter
00:05:35 like slash something but simply say I
00:05:38 want to handle every request that
00:05:41 reaches this line because if you reach
00:05:43 that line it means no route in one of
00:05:46 these two files was able to handle the
00:05:48 request so here in this middle of where
00:05:51 I again have my request response and the
00:05:53 next function and now I simply want to
00:05:57 return an error here so I will create a
00:06:00 new constant error and create a new
00:06:03 error here the error object is available
00:06:06 by default you don't need to import it
00:06:08 or anything like that and here I want to
00:06:12 output not found as a error text I will
00:06:17 also set a error status code excuse me
00:06:21 that should be error so that error
00:06:23 object is provided by no chase and I can
00:06:26 set a status code of 404 because here we
00:06:30 get here if we have an error because we
00:06:32 didn't find a fitting route which is the
00:06:34 definition of a 404 error then I will
00:06:37 actually execute this next method and
00:06:39 pass my error along with it this will
00:06:43 now forward the request but forward this
00:06:47 error request here instead of the
00:06:50 original one essentially now add another
00:06:53 middleware here where I also get my
00:06:57 request response and next but I get a
00:06:59 separate first argument which actually
00:07:02 is my error and this here will handle
00:07:06 all kinds of errors like the error we
00:07:09 create here and we for
00:07:11 word or and that is why I chose this
00:07:13 setup errors thrown from anywhere else
00:07:16 in this application this shouldn't
00:07:19 really be able to happen yet but later
00:07:21 when we add a database for example and
00:07:24 when we have operations doing work on
00:07:27 the database these operations could fail
00:07:29 and we then want to return a 500 error
00:07:33 now if these operations fail they will
00:07:35 directly throw an error so we don't make
00:07:38 it into this first middleware but since
00:07:41 they throw an error this middleware here
00:07:44 would be triggered and it would handle
00:07:47 this error or get this error so here we
00:07:49 can set a status code on the response we
00:07:52 eventually want to send back which is
00:07:54 either the status code the error has
00:07:57 like it has if we created our 400 error
00:08:00 404 error or we assign a 500 error code
00:08:05 for all other kinds of errors and then
00:08:08 we can simply return some JSON data here
00:08:11 and we could have changed that as I did
00:08:13 in the router setup so that would have
00:08:15 worked too and there I want to send an
00:08:18 error object which maybe should have a
00:08:21 message property and this setup is
00:08:24 totally up to you set it up as you want
00:08:26 and there I will pass on my error
00:08:30 message like the message this should
00:08:34 also be error by the way the a message
00:08:36 of the error we get as a first argument
00:08:38 here the message will automatically be
00:08:40 not found and for other errors
00:08:44 whoops fix the typo for our errors these
00:08:47 typically also have a message property
00:08:49 it's kind of what most errors have you
00:08:52 can pretty much rely on them having a
00:08:54 message object a message property and
00:08:57 now we will return this so let's try
00:09:01 this out let's save this and no daman
00:09:03 will restart and now let's again send an
00:09:06 invalid request now you see we get back
00:09:10 a method and our answer here error
00:09:14 status is not a function it nicely
00:09:16 proves that the automatically thrown
00:09:18 error has a message property because

00:09:21 that's not our own error and I did
00:09:23 indeed
00:09:24 is up here we should assign an error
00:09:26 status property of 404 not a method so
00:09:30 now let's try this again and now we get
00:09:33 not found which again is our custom
00:09:36 message this one and so I accidentally
00:09:40 but it's also kind of good I guess
00:09:41 proved that though our custom 404 and
00:09:46 ler SD I handle all other kinds of
00:09:49 errors like my error with the unknown
00:09:51 function here both work and with that we
00:09:55 got automatic reloading
00:09:56 we got default logging and we got error
00:09:59 handling which is a great improvement to
00:10:01 our project with that let's leave it as
00:10:05 this and let's go back into our project
00:10:08 and make sure that we add more useful
00:10:11 functionalities to it in the next videos

You may also like