1 00:00:00,540 --> 00:00:07,350 Once we have set up the async rapper next, I want to work on catching the errors and we're going to 2 00:00:07,350 --> 00:00:11,040 start our journey actually in the express documentation. 3 00:00:11,340 --> 00:00:17,370 So it goes to ExpressJet dot com online in search box, just type error. 4 00:00:17,760 --> 00:00:20,730 And first, let's take a look at the default one. 5 00:00:20,970 --> 00:00:26,370 And if you take a look at the first sentence, Xpress comes with built in error handler that takes care 6 00:00:26,370 --> 00:00:29,460 of any errors that might be encountered in the app. 7 00:00:29,730 --> 00:00:36,120 This default error handling middleware function is added at the end of the middleware function stack. 8 00:00:36,510 --> 00:00:45,390 And if we pass in error to the next and you do not handle it in a custom handler, it will be handled 9 00:00:45,390 --> 00:00:46,700 by the built in one. 10 00:00:47,010 --> 00:00:48,300 Why am I telling you this? 11 00:00:48,300 --> 00:00:50,880 Well, because that answers this question. 12 00:00:51,210 --> 00:00:53,410 Where is this response coming from? 13 00:00:53,700 --> 00:00:57,630 Well, that is coming from the default built in error handler. 14 00:00:57,930 --> 00:00:59,760 That's point number one I want to make. 15 00:01:00,030 --> 00:01:04,830 Otherwise you might be wondering, well, where are we getting this info second next. 16 00:01:04,830 --> 00:01:05,310 Correct. 17 00:01:05,519 --> 00:01:10,320 That's why in the async wrapper we set up this next an error. 18 00:01:10,950 --> 00:01:13,280 So we pass that to the next middleware. 19 00:01:13,290 --> 00:01:17,550 But in our case, of course, we haven't set up that handler yet. 20 00:01:17,850 --> 00:01:22,100 So therefore, it was just eventually passed down to the built in one. 21 00:01:22,440 --> 00:01:26,880 And lastly, if we go back and if we say here, so I'll search one more time. 22 00:01:27,120 --> 00:01:30,660 And in this case, we're looking for writing error handlers. 23 00:01:31,020 --> 00:01:32,460 So this is what we're about to do. 24 00:01:32,760 --> 00:01:35,190 We'll set up another set of middleware. 25 00:01:35,190 --> 00:01:39,690 However, in this case, the middleware will handle errors. 26 00:01:40,050 --> 00:01:45,780 And you can see that if we want to handle errors, we just pass in for arguments. 27 00:01:46,050 --> 00:01:53,540 And then the first one, we will be that error and we want to play that at the very end of our road. 28 00:01:53,880 --> 00:01:55,290 So let's just navigate back. 29 00:01:55,560 --> 00:02:01,590 And of course, in the example, they showcase how they right away set up the middleware in the app. 30 00:02:01,590 --> 00:02:09,090 Just in our case, since we'll have more code, essentially, I want to create another file in the middle 31 00:02:09,090 --> 00:02:10,360 or so in here. 32 00:02:10,410 --> 00:02:15,690 I'm just looking for new file and I'll call this error and then handler. 33 00:02:15,840 --> 00:02:20,520 And instead of the file, I just need to come up with the function and I'm going to go the longer out 34 00:02:20,550 --> 00:02:24,510 where else say Error and Lir middleware. 35 00:02:24,510 --> 00:02:25,970 And that is equal to error. 36 00:02:26,130 --> 00:02:30,900 Again, in this case, we need to have four parameters, request response. 37 00:02:31,200 --> 00:02:33,270 And we also have next. 38 00:02:33,450 --> 00:02:40,290 And as far as the logic will add more code once we set up our own custom, our class. 39 00:02:40,560 --> 00:02:46,110 But for the time being, we just want to go with a return and rise of that status. 40 00:02:46,110 --> 00:02:50,820 And if you remember, that's exactly what we had previously in the try catch block. 41 00:02:51,030 --> 00:02:57,790 And I'm just going to go five hundred and we'll say JSON error and error is equal to error. 42 00:02:57,960 --> 00:03:02,520 Now if you want, you can come to log out, of course, but the result is going to be exactly the same. 43 00:03:02,520 --> 00:03:09,750 Where in here we'll have access to that error, the one that is going to be coming in our case from 44 00:03:09,750 --> 00:03:11,160 this async wrapper. 45 00:03:11,400 --> 00:03:13,710 And then we just need to decide what we want to do. 46 00:03:13,890 --> 00:03:19,800 And I'll just start by saying error equal to her and you're not actually, I want to go with message 47 00:03:20,070 --> 00:03:21,270 is equal to error. 48 00:03:21,600 --> 00:03:26,550 And now we simply want to go back to abcess, where we have not found. 49 00:03:26,700 --> 00:03:30,150 We just copy and paste and now we just need to come up with a name. 50 00:03:30,390 --> 00:03:34,620 And as you know, naming is probably the hardest thing in programming. 51 00:03:34,980 --> 00:03:39,270 So I'm just going to call this error handler and then middleware. 52 00:03:39,600 --> 00:03:46,140 And of course, that one is coming from the file that we just set up, the error handler, and then 53 00:03:46,140 --> 00:03:47,970 we want to scroll all the way down. 54 00:03:48,270 --> 00:03:51,390 And right after not found, we're going to go with abduct use. 55 00:03:51,660 --> 00:03:59,040 And of course, we'll pass in the error handler Middlemore And once we save and we go back to the postman 56 00:03:59,370 --> 00:04:07,800 and try to send the same request, meaning the request with a incomplete data, then we should get a 57 00:04:07,800 --> 00:04:08,580 different response. 58 00:04:08,580 --> 00:04:10,140 But we don't effectively. 59 00:04:10,140 --> 00:04:11,520 It looks like I have a bug. 60 00:04:11,850 --> 00:04:13,590 So let me check the error handler. 61 00:04:13,830 --> 00:04:16,800 And yes, of course, I didn't export the function. 62 00:04:16,800 --> 00:04:19,470 So let me go with module sports. 63 00:04:19,649 --> 00:04:22,350 And that one is equal to a handler one. 64 00:04:22,650 --> 00:04:28,860 And of course, if I tested out right now, I should see the customer response and we can clearly see 65 00:04:28,860 --> 00:04:31,080 that because we have the message. 66 00:04:31,080 --> 00:04:37,230 Now, like I already mentioned previously, if you don't like these big, massive error messages, you 67 00:04:37,230 --> 00:04:38,910 can simply go back over here. 68 00:04:39,090 --> 00:04:45,510 And instead of sending the message equal to an error, you can just hard code some kind of message so 69 00:04:45,510 --> 00:04:48,810 you can go something along the lines of something. 70 00:04:49,860 --> 00:04:56,190 Something went wrong, karma, try again later. 71 00:04:57,390 --> 00:05:04,800 This is what we'll see in Afghanistan and of course, our message ish or so, essentially, this is 72 00:05:04,800 --> 00:05:12,240 how we can set up a custom Arab handler in Xpress where we add another piece of middleware and that 73 00:05:12,240 --> 00:05:14,700 in there we have four arguments on. 74 00:05:14,700 --> 00:05:16,710 The first one is going to be the era. 75 00:05:16,980 --> 00:05:23,340 And of course, in our case, the way we passed the errors down to this custom, our handler is by using 76 00:05:23,340 --> 00:05:26,790 the async wrapper and in there we have the next. 77 00:05:27,030 --> 00:05:31,290 So as you remember from the Turrill with next, we pass it to the next middleware. 78 00:05:31,590 --> 00:05:34,190 And previously we use the built in default one. 79 00:05:34,410 --> 00:05:39,120 And now, of course, we have our own where effectively you can set up whatever logic you want. 80 00:05:39,300 --> 00:05:43,290 If you want to send us as two hundred, nothing stops you from doing that. 81 00:05:43,590 --> 00:05:50,010 But of course, a more meaningful response would be with some kind of error code, with some kind of 82 00:05:50,010 --> 00:05:57,030 meaningful message, whether that is hard coded string or you can pass and the entire error object.