WEBVTT 00:03.790 --> 00:05.230 Hey did everyone that they share. 00:05.230 --> 00:08.650 And welcome to another video of the pro back end developer course. 00:08.770 --> 00:13.240 Now our application is looking good and it's fine and we can definitely move forward in building the 00:13.240 --> 00:14.080 application. 00:14.080 --> 00:16.960 But of course the goal is not to build that toy application. 00:16.960 --> 00:20.560 The goal is to understand the in depth of what we're trying to achieve here. 00:20.650 --> 00:25.690 Now, two new keywords are right in front of us, the first one being request and the second one being 00:25.690 --> 00:26.430 response. 00:26.440 --> 00:31.120 In fact, many of the time you are going to see that there is something like a next or there is a whole 00:31.120 --> 00:32.170 lot of things that goes on. 00:32.170 --> 00:36.970 But right now the goal is really simple that I want to understand more in-depth about request and the 00:36.970 --> 00:37.810 response. 00:37.820 --> 00:40.270 Now, the request is something which we have already seen. 00:40.270 --> 00:45.970 This can be a type of get post put and delete and a little bit more, but this is all the requests that 00:45.970 --> 00:48.160 you are trying to make to the server. 00:48.160 --> 00:52.900 And not only just you can take some things like that, you have type to search on, you can take a lot 00:52.900 --> 00:56.230 of information to the server at the time of requesting it. 00:56.260 --> 01:01.930 Similarly, server can respond and server response you in the form of response, also known as this 01:01.930 --> 01:02.560 rest. 01:02.560 --> 01:05.020 And this is how we are sending back this data. 01:05.020 --> 01:07.660 But we need a little bit more in-depth analysis of that. 01:07.660 --> 01:12.700 And this analysis and this study is going to depend on what kind of framework you are choosing on. 01:12.700 --> 01:13.900 We are choosing EXPRESS. 01:13.900 --> 01:16.930 So we're going to study the Express documentation in case you choose something else. 01:16.930 --> 01:21.070 Obviously have to study different, but after this course, okay, let's move on. 01:21.070 --> 01:23.710 So this is the basics and let's go up here. 01:24.010 --> 01:26.380 So first, let's talk about how this is happening. 01:26.380 --> 01:29.320 So Web request in response, we have already gone through that request. 01:29.320 --> 01:35.050 Is there as soon as you make a request on the Web, the Web starts analyzing that request process, 01:35.050 --> 01:40.660 that request, maybe grab some data from the database and then finally it gets you a response back. 01:40.660 --> 01:46.240 But not only just response, it also sometimes gets you a status or also known as status code. 01:46.270 --> 01:47.470 This is really important. 01:47.470 --> 01:54.220 This is the information that is important to write better APIs or as well as formal APIs or the production 01:54.220 --> 01:55.300 grade APIs. 01:55.300 --> 01:59.770 Let's go ahead and obviously I have a link for you to explore on these Web requests. 01:59.770 --> 02:01.450 So let's go ahead and open this up. 02:01.450 --> 02:04.000 So this is the HTTP response status code. 02:04.000 --> 02:05.680 You don't need to memorize any of it. 02:05.680 --> 02:11.680 There are only a handful of few which we use, but if you know a lot more, that is always great. 02:11.680 --> 02:17.890 So for all the information, informational response we use between 100 to 199, I'll explain more in 02:17.890 --> 02:21.940 detail what those are for successful response 202 to 99. 02:21.940 --> 02:26.110 This is usually the range you are going to be mostly using 200 or 201. 02:26.110 --> 02:28.000 Then there is a redirection message. 02:28.000 --> 02:31.840 You won't be using too much of the 300 codes 405 hundred code. 02:31.840 --> 02:36.340 You'll be using 400 code for when a client gives you something wrong. 02:36.340 --> 02:41.470 Information for something like a wrong email or something like this or the password doesn't match. 02:41.470 --> 02:45.400 We use a range of 400 code and then 500 code. 02:45.400 --> 02:49.780 Now the good thing is these codes are not kind of governance bodies. 02:49.780 --> 02:54.940 You can decide that whatever the code you want to return, of course you can return for all successful 02:54.940 --> 02:58.960 message 200 code, but nobody is stopping you to return a 400 code. 02:58.960 --> 03:03.220 Of course it would be bad for the API design, but nobody's stopping you to do so. 03:03.250 --> 03:04.210 I am stopping you. 03:04.210 --> 03:04.960 Please don't do this. 03:04.960 --> 03:05.950 This is really bad. 03:06.360 --> 03:08.140 A couple of ones which I would like to introduce. 03:08.140 --> 03:12.760 You don't need to remember all of them for all the get head put, body trace, all kinds of this you'll 03:12.760 --> 03:13.960 be mostly using 200. 03:13.960 --> 03:15.550 200 means everything is okay. 03:15.550 --> 03:16.870 It was successful. 03:16.900 --> 03:22.060 Now it is recommended that for all the post input request you send at 201, whenever there is a new 03:22.060 --> 03:27.160 record being created in the database, you'll find that majority of the Pro-level organization use this 03:27.160 --> 03:29.350 specific code, so make sure you remember that. 03:29.350 --> 03:34.570 But in the majority of the applications and videos and courses, we actually tend to use 200 more. 03:34.570 --> 03:35.740 And this is all okay. 03:35.740 --> 03:37.420 This is not bad at all. 03:37.420 --> 03:41.110 Now in the 300 you won't be using too much of the redirections of the code. 03:41.110 --> 03:43.630 Something like 300 not found in all of that. 03:43.630 --> 03:47.710 So these are rarely used, but most of the time you'll be using 400. 03:47.710 --> 03:50.740 These are for client requests, like bad request. 03:50.740 --> 03:54.670 Or maybe somebody is trying to access a resource which is not authorized for him. 03:54.670 --> 03:56.410 The payment for or to nobody. 03:56.410 --> 03:59.560 I've seen ever you using this one so I don't know. 03:59.920 --> 04:01.210 It might be used somewhere. 04:01.210 --> 04:07.360 403 is almost similar to 401, but this is forbidden for every one resource and stuff like that. 04:07.360 --> 04:10.390 500 is definitely when something goes wrong onto the server. 04:10.390 --> 04:13.390 So you're going to see scrolling a little bit something like Bad Gateway. 04:13.390 --> 04:18.580 You might have seen this many times and internal server error, of course, a famous one now one of 04:18.580 --> 04:20.290 the common one is 4 to 4. 04:20.290 --> 04:24.490 I'm pretty sure that most of you might be familiar with the 404 not found. 04:24.490 --> 04:28.420 When you don't find the resource on the server again, you don't need to memorize all of them. 04:28.420 --> 04:31.060 Just remember that 200 and 201 are okay. 04:31.060 --> 04:33.520 Responses 404 is not found. 04:33.520 --> 04:37.420 400 is just basically there is something wrong from the client side. 04:37.690 --> 04:39.910 So something like bad request or something. 04:39.910 --> 04:44.620 And 401 is unauthorized 500 is something went wrong from our site on the server. 04:44.620 --> 04:46.900 These are the basic ones that you have to remember. 04:47.320 --> 04:51.190 So this is the basics now coming back onto the express. 04:52.000 --> 04:55.120 Now this time we'll be going a little bit more than the getting started. 04:55.120 --> 04:55.690 This guide. 04:55.690 --> 04:58.630 We need to understand how the APIs of Express works. 04:58.630 --> 05:00.910 Yes, they have their own APIs as well. 05:01.030 --> 05:01.450 So let's. 05:01.500 --> 05:03.870 Go on to the five X because that's what we are using. 05:03.870 --> 05:08.040 And again, in case you want to get more detail which one you should be looking for, you can go ahead 05:08.040 --> 05:08.880 and look for that. 05:08.880 --> 05:10.890 We are using a 4.71. 05:10.890 --> 05:14.340 So of course the version five is not yet being released. 05:14.340 --> 05:17.580 So you might be looking for the four x, not the five x. 05:17.580 --> 05:21.840 So let's go ahead and look for four X in case you want to check out the five x, this is exactly how 05:21.840 --> 05:22.830 you would be doing. 05:22.920 --> 05:26.010 So here we can see we have a request and we have a response. 05:26.010 --> 05:28.590 First, let's see what all we can do in the request. 05:28.590 --> 05:31.530 So you can see there is a whole lot of things that can come up in the request. 05:31.530 --> 05:37.050 You can access the body, you can access the base URL, you can access cookies, you can access host 05:37.050 --> 05:37.530 name. 05:37.530 --> 05:39.150 There's a whole lot that we can do here. 05:39.150 --> 05:40.830 There is a path, there is params. 05:40.830 --> 05:42.690 I will explain them in more detail. 05:42.690 --> 05:45.210 There is a query route, signed cookies. 05:45.210 --> 05:47.370 There's a whole lot that comes up with the request. 05:47.460 --> 05:52.380 And of course, I know many of you didn't realize this, but yes, cookies and parameters and token, 05:52.380 --> 05:58.200 even when you reset your password or you access the email first time and you create an account and say, 05:58.200 --> 06:03.000 hey, I'm authorized, this is all been coming up in the token from the URL itself and this all comes 06:03.000 --> 06:03.870 from the request. 06:03.870 --> 06:04.770 So this is it. 06:04.980 --> 06:09.990 And when it comes to the response, this is where the response comes in or response from the server 06:09.990 --> 06:13.440 side is being sent to anybody who is requesting it. 06:13.440 --> 06:18.810 So you can send headers and this is the most common one and you can also go ahead and use something 06:18.810 --> 06:22.500 like resource send that we just use, which is somewhere here. 06:22.500 --> 06:27.630 There we go, restart, send and this is what we have been using, resort send and we send up some paragraph 06:27.630 --> 06:28.380 or something like that. 06:28.380 --> 06:29.910 So this is where it is coming up. 06:30.000 --> 06:35.610 You can also send raised or JSON and we can send the JSON data which we'll be sending up in a minute 06:35.610 --> 06:36.600 and all of that. 06:37.050 --> 06:39.450 But there is an important one which you are going to see. 06:39.450 --> 06:42.960 There is a red dot send status and resource status. 06:42.960 --> 06:49.500 So I told you status is for raising something like four or three, 400, whatever the status is, but 06:49.500 --> 06:53.490 very similar of that which is red dot send status. 06:53.490 --> 06:57.840 So what's the difference between the resort status and resort send status? 06:58.260 --> 07:01.440 Not too much resident status send status. 07:01.440 --> 07:06.000 Actually, you not only just send the status, you actually bind it up with a little bit more. 07:06.000 --> 07:07.950 Like you can see that as dot status. 07:08.190 --> 07:12.930 When you want to simply say send status, that means I only want to send the status, just the code 07:12.930 --> 07:16.620 400 300 201, whatever. 07:16.620 --> 07:21.840 But when I use something like resident status, then I can just use the status to send the status, 07:21.840 --> 07:27.150 but I can also chain on this dot send to send whatever the request is that I'm sending you. 07:27.150 --> 07:30.240 And again, all you have to do is come up here and read that. 07:30.240 --> 07:35.430 For example, if you want to set some cookies, you have to say it as dot cookie and stuff like that. 07:35.430 --> 07:37.020 So that's all what we do. 07:37.050 --> 07:41.310 Now, let's go ahead and modify our request that we have sent to make it a little bit more professional. 07:41.310 --> 07:42.660 Not too much, but a little bit. 07:42.660 --> 07:48.390 So I can simply say resident status and this time we are sending up an okay request. 07:48.390 --> 07:53.340 So 200, everything is okay and then I can chain on a dot send and everything like that. 07:53.340 --> 07:58.950 If I save this you can see server is still up and running and our browser is not going to make any difference. 07:58.950 --> 08:01.140 And that's where the postman comes in. 08:01.230 --> 08:05.010 This is exactly the time where you see that what request comes up. 08:05.010 --> 08:07.260 So let me go ahead and fire up my postman. 08:07.350 --> 08:08.370 And there we go. 08:08.970 --> 08:11.430 It's going to take a little bit of the time. 08:11.430 --> 08:12.480 There we go. 08:13.380 --> 08:15.420 And come on, you can do this. 08:16.550 --> 08:17.850 And I'm going to just open up a new. 08:17.900 --> 08:18.470 Just open up. 08:18.470 --> 08:21.230 Just close all of these guys and just open up a new tab. 08:21.230 --> 08:23.000 And it will open up a new request for you. 08:23.030 --> 08:26.840 You might be up here somewhere and just click on this plus icon and you'll be getting that. 08:26.870 --> 08:30.370 Let's go ahead and use the local host for 1000 and a slash. 08:30.380 --> 08:32.450 And of course, you can choose all of your get posts. 08:32.480 --> 08:37.390 There is a whole lot that it allows you, but we'll be just going for the get as soon as I send this 08:37.400 --> 08:43.220 the notice here it says here, start us 200 OC and it says a response of Hello World. 08:43.250 --> 08:47.770 Now let's go ahead and try to change this response to just see that RV on the same page or not. 08:47.780 --> 08:53.120 If I go ahead and say 201, which is not really an ideal status code in this case, but if I try to 08:53.120 --> 08:58.550 go ahead and send this now, I say to a one created now nothing has been created, but I told you, 08:58.550 --> 08:59.960 nobody's stopping you to do so. 08:59.960 --> 09:04.850 But this is where the status code is responsible and where it is being used at the time. 09:04.850 --> 09:09.980 When somebody is working on the front end, they will be proceeding further based on the status code. 09:09.980 --> 09:14.420 If the status code is 400, there's no point of moving further because something is wrong. 09:14.420 --> 09:19.490 If the status code is 200, that means everything is okay and I can proceed further off however I have 09:19.490 --> 09:20.270 planned on. 09:20.270 --> 09:25.220 So status code are really important and it is recommended that if you're creating a pro grade or production 09:25.220 --> 09:28.700 grade application, you should always put the status code. 09:28.820 --> 09:29.980 That's it for this video. 09:30.020 --> 09:31.520 Let's catch up in the next one.