1 00:00:00,300 --> 00:00:01,500 In this video. 2 00:00:01,500 --> 00:00:08,160 Let's see how we can catch any error that might occur inside our route. 3 00:00:08,280 --> 00:00:15,630 In a previous video, we were able to catch any error that might occur outside our route, and that 4 00:00:15,630 --> 00:00:18,000 is for for error handling. 5 00:00:18,090 --> 00:00:25,370 So let's forecast the kind of error that might occur inside any route before we continue. 6 00:00:25,410 --> 00:00:30,870 Let's create one more dummy route and this one going to be profile. 7 00:00:31,260 --> 00:00:33,150 So here I'll change this one. 8 00:00:33,150 --> 00:00:36,480 To slash profile is a get request. 9 00:00:36,480 --> 00:00:39,960 And this one also adds profile. 10 00:00:39,960 --> 00:00:42,000 And welcome to your. 11 00:00:42,750 --> 00:00:44,820 Profile page. 12 00:00:45,210 --> 00:00:53,940 So what you are going to do is that inside the profile route here, we are going to check if a user 13 00:00:53,940 --> 00:00:55,230 is logged in. 14 00:00:55,230 --> 00:01:00,420 If you are logged in, then you are going to display this message to you. 15 00:01:00,600 --> 00:01:06,030 Otherwise, we are going to send a message by saying that please log in first. 16 00:01:06,030 --> 00:01:08,270 So how are you going to implement that? 17 00:01:08,280 --> 00:01:12,270 Well, we are going to mimic real log in system here. 18 00:01:12,270 --> 00:01:14,790 So let's see how we are going to implement that. 19 00:01:14,820 --> 00:01:22,860 Let's assume that we are getting this user from database so we can say that let's is logged in equal 20 00:01:22,860 --> 00:01:23,940 to true. 21 00:01:24,510 --> 00:01:28,050 So let's check if the user is not logged in. 22 00:01:28,050 --> 00:01:30,120 So here is the logic. 23 00:01:30,240 --> 00:01:39,660 If it's not logged in, then we are going to return from this function by passing in a new error message 24 00:01:39,660 --> 00:01:42,180 to the error constructor function. 25 00:01:42,180 --> 00:01:45,900 I'll start and we will say that please. 26 00:01:46,870 --> 00:01:48,930 Look in first. 27 00:01:48,940 --> 00:01:51,880 So now let's see back to the request. 28 00:01:51,910 --> 00:01:57,450 Now I'm going to make use of slash profile and hit send. 29 00:01:57,460 --> 00:02:01,240 And you can see that when come to your profile page. 30 00:02:01,270 --> 00:02:05,140 It simply means that it's logged in is true. 31 00:02:05,740 --> 00:02:09,280 So let's change this one to false. 32 00:02:09,550 --> 00:02:11,450 Now, here we go. 33 00:02:11,470 --> 00:02:13,690 Let's try to make the request. 34 00:02:13,690 --> 00:02:20,290 And now you can see that there is no response, meaning that the user is not log in. 35 00:02:20,290 --> 00:02:23,100 So this message is not returning. 36 00:02:23,110 --> 00:02:27,820 So the question is, how can we have access to this message? 37 00:02:27,880 --> 00:02:30,850 That is why we have next here. 38 00:02:31,000 --> 00:02:39,790 So anything that we pass into next, then Express was regarded as an error and then it's going to give 39 00:02:39,790 --> 00:02:42,190 it to the built in error handler. 40 00:02:42,370 --> 00:02:48,820 So now instead of this returning something like this, we are going to pass in the entire message to 41 00:02:48,820 --> 00:02:49,500 next. 42 00:02:49,510 --> 00:02:57,580 So let's cut this message and then we bring in next and then we paste in our message as that when we 43 00:02:57,580 --> 00:02:58,270 save it. 44 00:02:58,270 --> 00:03:01,060 Now let's make the request again. 45 00:03:01,060 --> 00:03:09,340 And this time around we have something incredible, meaning that place logged in because we have through 46 00:03:09,340 --> 00:03:16,740 an error inside our route where we pass to the next and next will pass into the built in error handler. 47 00:03:16,750 --> 00:03:20,430 And that's why we have this beautiful message. 48 00:03:20,440 --> 00:03:25,300 But we can see this is almost the same as the one we did before. 49 00:03:25,300 --> 00:03:27,370 But this time around it is not full. 50 00:03:27,400 --> 00:03:32,380 Oh four, but instead is a logic that is inside our route. 51 00:03:32,380 --> 00:03:35,440 So how can we have access to this error? 52 00:03:35,440 --> 00:03:38,010 And then we can send a beautiful message. 53 00:03:38,020 --> 00:03:43,840 That is why Express has given us a global error handling method. 54 00:03:43,840 --> 00:03:49,630 So for us to send beautiful message or custom message, we are going to use this global. 55 00:03:50,750 --> 00:03:52,340 Error handling. 56 00:03:53,290 --> 00:03:54,220 Middle. 57 00:03:55,720 --> 00:03:58,110 Well, and here it goes. 58 00:03:58,120 --> 00:04:06,340 We bring in app dot use and for use you pass in the callback function and for the callback function 59 00:04:06,340 --> 00:04:13,150 we have access to error, the request objects, the response and then the next. 60 00:04:13,390 --> 00:04:21,190 So the error argument contains the error that we pass in to next, and then the request contains our 61 00:04:21,190 --> 00:04:23,800 request object likewise response. 62 00:04:23,800 --> 00:04:25,300 And then next. 63 00:04:25,300 --> 00:04:31,840 So any time Express sees this kind of middleware, it means that we are trying to catch an error. 64 00:04:31,870 --> 00:04:41,410 So if you try to console the log, the error here, now let's check our terminal here and let's make 65 00:04:41,410 --> 00:04:49,090 the requests and let's send this time around, we can see that we have an error code place logged in. 66 00:04:49,090 --> 00:04:53,740 So how can we send a beautiful message for sending response? 67 00:04:53,740 --> 00:04:57,310 We need to send at least this three properties. 68 00:04:57,310 --> 00:05:01,150 One is the status code of the response. 69 00:05:01,270 --> 00:05:06,880 The next property that we want to send to the user is what we call the status. 70 00:05:06,880 --> 00:05:15,010 So this one, we can provide our custom message, for example, failed or success. 71 00:05:15,220 --> 00:05:17,170 So this one is up to us. 72 00:05:17,170 --> 00:05:22,630 And lastly is the actual message that we want to send for status code. 73 00:05:22,630 --> 00:05:25,840 We can send a message something like four or four. 74 00:05:26,110 --> 00:05:33,340 So any response that we send to the user, whether success or failure, try to send these three properties. 75 00:05:33,340 --> 00:05:39,400 So we are going to send this property to the user, but for the message, it's going to be an error. 76 00:05:39,490 --> 00:05:48,520 But before we continue, we have access to the error, which is this one on a property called message. 77 00:05:48,520 --> 00:05:50,740 So let me show you before we continue. 78 00:05:50,770 --> 00:05:55,960 So if you console.log the error dot. 79 00:05:57,150 --> 00:05:58,740 Darts message. 80 00:05:58,770 --> 00:06:04,260 Now, if you save it now, let's check our terminal here and let's make the requests. 81 00:06:05,680 --> 00:06:14,250 Now you can see that we have the message called Please Locked in so we can use that one as a message. 82 00:06:14,260 --> 00:06:20,200 So now inside our error handling here, let's try to send a beautiful message. 83 00:06:20,200 --> 00:06:21,910 So here we go. 84 00:06:21,910 --> 00:06:25,840 So let's go ahead and send the response to the user. 85 00:06:25,870 --> 00:06:33,220 The first property you want to send is what we call the status code that is status like that, and then 86 00:06:33,220 --> 00:06:34,900 we pass the code. 87 00:06:34,900 --> 00:06:39,910 So now here comes how will I know the kind of code we want to send? 88 00:06:40,180 --> 00:06:44,860 This website contains all the status code with it meaning? 89 00:06:44,860 --> 00:06:55,300 And I'll provide for you and for this it has been categorized and our information, our successful redirection 90 00:06:55,840 --> 00:07:04,990 client error and server error for server error is start from five and then for client error is start 91 00:07:04,990 --> 00:07:10,030 from four and then for redirection is start from three. 92 00:07:10,030 --> 00:07:15,640 Likewise successful that is two and then information that is one here. 93 00:07:15,640 --> 00:07:23,530 So what we want is what you call client error, which means unauthorized or bad requests or forbidden. 94 00:07:23,530 --> 00:07:27,970 So we can use any of this one, but let's use 401, which means what? 95 00:07:27,970 --> 00:07:29,140 Unauthorized. 96 00:07:29,140 --> 00:07:37,030 So now let's get back to the error handler here and here you provide in here as 401 and then the next 97 00:07:37,030 --> 00:07:38,650 one going to be the JSON. 98 00:07:38,650 --> 00:07:41,500 And for this we can pass in any message. 99 00:07:41,500 --> 00:07:44,230 But what we want right now is the status. 100 00:07:44,230 --> 00:07:46,360 So here we provide status. 101 00:07:46,360 --> 00:07:48,820 It can be anything, the property. 102 00:07:50,400 --> 00:07:52,980 And you say that failed. 103 00:07:53,190 --> 00:08:02,370 And then lastly, it's going to be the actual message and here we go is going to be as word error. 104 00:08:02,490 --> 00:08:10,260 And we have access to the message on the property code message, which is the this one. 105 00:08:10,260 --> 00:08:13,370 So with this one, we are all set. 106 00:08:13,380 --> 00:08:16,230 So let's go ahead and then make the request again. 107 00:08:16,260 --> 00:08:17,490 Now have a look. 108 00:08:17,520 --> 00:08:21,660 This time around we have something incredible failed. 109 00:08:21,660 --> 00:08:23,070 Please log in. 110 00:08:23,250 --> 00:08:31,560 So any message that I'll pass in to this one, I'm going to receive it so I can change this one to you 111 00:08:31,560 --> 00:08:34,620 are not logged in. 112 00:08:34,620 --> 00:08:37,530 So again, let's save it and make the request. 113 00:08:37,530 --> 00:08:40,500 And again, you can see that you are not logged in. 114 00:08:40,620 --> 00:08:44,490 So inside the home root, let's say that we have some network issues. 115 00:08:44,490 --> 00:08:51,240 So we say network is live and by default I would say false. 116 00:08:51,570 --> 00:08:59,970 And then we can say that if there is no network, then we can go ahead, return from this function and 117 00:08:59,970 --> 00:09:02,310 then we pass in the error. 118 00:09:02,340 --> 00:09:08,400 You would say that no network, save it and let's make the requests where you can see that there is 119 00:09:08,400 --> 00:09:13,280 no message simply because I need to pass the error to the error class. 120 00:09:13,280 --> 00:09:19,320 So we're going to be name error and then I'll pass in the error. 121 00:09:19,350 --> 00:09:25,290 This time around, you're going to have access to the error and here we go. 122 00:09:25,380 --> 00:09:26,130 Good. 123 00:09:26,130 --> 00:09:27,450 So that is about it. 124 00:09:27,450 --> 00:09:29,130 But guys, look at this one. 125 00:09:29,160 --> 00:09:36,990 We still have what is called unauthorized for or for, even though this one is not authorization but 126 00:09:36,990 --> 00:09:38,370 network issue. 127 00:09:38,960 --> 00:09:44,210 So how can we send a specific status code based on the type of error? 128 00:09:44,540 --> 00:09:52,550 So in the next video, we are going to modify this one a little bit so that it can accept any type of 129 00:09:52,550 --> 00:09:55,460 message with different type of status code. 130 00:09:55,700 --> 00:09:59,960 Where I made some typing error here is supposed to be global. 131 00:10:00,170 --> 00:10:00,560 All right. 132 00:10:00,560 --> 00:10:04,790 So let's go ahead and then modify this middleware in the next video.