1 00:00:02,120 --> 00:00:04,500 Now, before we now take a closer look 2 00:00:04,500 --> 00:00:06,710 at cookies and sessions again, 3 00:00:06,710 --> 00:00:09,560 I want to implement the logout functionality, 4 00:00:09,560 --> 00:00:12,320 because at the moment that is not working 5 00:00:12,320 --> 00:00:13,630 and to make it work, 6 00:00:13,630 --> 00:00:16,460 we have to think about what should happen 7 00:00:16,460 --> 00:00:17,743 if we click Logout. 8 00:00:18,660 --> 00:00:20,870 Well, what happens at the moment 9 00:00:20,870 --> 00:00:25,750 is that this logout post route here is reached 10 00:00:25,750 --> 00:00:27,670 or it should be reached, 11 00:00:27,670 --> 00:00:30,010 because if I have a look at my header 12 00:00:30,010 --> 00:00:31,720 for this Logout button, 13 00:00:31,720 --> 00:00:34,870 it's in a form because I want to send a POST request 14 00:00:34,870 --> 00:00:37,660 because since we change something on the server 15 00:00:37,660 --> 00:00:38,600 in the database, 16 00:00:38,600 --> 00:00:41,980 it makes more sense to me to use a POST request. 17 00:00:41,980 --> 00:00:45,043 And it is a POST request send to /logout. 18 00:00:46,640 --> 00:00:49,450 Now to make sure that something happens 19 00:00:49,450 --> 00:00:53,750 in this post logout route here, which already was prepared, 20 00:00:53,750 --> 00:00:57,640 we in the end want to delete that authentication data 21 00:00:57,640 --> 00:01:01,490 from the session because it's the existence of this data 22 00:01:01,490 --> 00:01:04,980 that grants us access to the protected resources. 23 00:01:04,980 --> 00:01:09,850 We check for isAuthenticated and/or the user here. 24 00:01:09,850 --> 00:01:12,760 So if we cleared that data from the session, 25 00:01:12,760 --> 00:01:14,240 the user, the visitor, 26 00:01:14,240 --> 00:01:16,320 who's trying to access a certain page, 27 00:01:16,320 --> 00:01:18,553 won't be able to do so anymore. 28 00:01:19,890 --> 00:01:23,560 We could also delete the entire session object 29 00:01:23,560 --> 00:01:26,860 from the database and therefore clear to cookie, 30 00:01:26,860 --> 00:01:29,430 but you should think twice about 31 00:01:29,430 --> 00:01:31,330 whether you want to do that or not, 32 00:01:31,330 --> 00:01:33,050 because as mentioned before, 33 00:01:33,050 --> 00:01:37,140 sessions can also be used for storing other data. 34 00:01:37,140 --> 00:01:39,130 One of the most prominent examples 35 00:01:39,130 --> 00:01:41,060 would be the shopping cart, 36 00:01:41,060 --> 00:01:43,030 which you might want to store 37 00:01:43,030 --> 00:01:45,770 even for unauthenticated users. 38 00:01:45,770 --> 00:01:48,860 That's a behavior you know from Amazon and so on as well. 39 00:01:48,860 --> 00:01:51,630 There you can add items to your shopping cart 40 00:01:51,630 --> 00:01:53,930 without being authenticated. 41 00:01:53,930 --> 00:01:57,650 So deleting the overall session is something you could do, 42 00:01:57,650 --> 00:02:00,570 but you typically don't want to do that. 43 00:02:00,570 --> 00:02:03,360 Instead, here in the logout route, 44 00:02:03,360 --> 00:02:08,169 I will simply reach out to my session and set user to null. 45 00:02:08,169 --> 00:02:10,930 And with that, I will effectively clear it. 46 00:02:10,930 --> 00:02:14,490 Null is also a built-in value in JavaScript 47 00:02:14,490 --> 00:02:16,800 that will be treated as a falsy 48 00:02:16,800 --> 00:02:19,310 if you would see it in a if check. 49 00:02:19,310 --> 00:02:22,420 So that will clear the user data from there. 50 00:02:22,420 --> 00:02:27,420 And I will set the isAuthenticated key to false 51 00:02:27,560 --> 00:02:30,950 because this user isn't authenticated anymore. 52 00:02:30,950 --> 00:02:33,850 Alternatively, we could also set this to null 53 00:02:33,850 --> 00:02:36,260 because this would also be treated as falsy, 54 00:02:36,260 --> 00:02:38,390 but since it is a Boolean already, 55 00:02:38,390 --> 00:02:40,143 I'll just set it to false. 56 00:02:41,870 --> 00:02:45,030 And then I want to redirect the user 57 00:02:45,030 --> 00:02:46,673 back to the starting page. 58 00:02:47,730 --> 00:02:51,720 Now we could again, save the session as we did it here 59 00:02:51,720 --> 00:02:54,410 when we first logged the user in 60 00:02:54,410 --> 00:02:58,160 and only redirect once we know that saving worked, 61 00:02:58,160 --> 00:03:00,820 but I only to do it like this here 62 00:03:00,820 --> 00:03:04,480 because I wanted to redirect the user to a page 63 00:03:04,480 --> 00:03:08,180 that relied on that session data being stored, 64 00:03:08,180 --> 00:03:10,180 because I redirected to a page 65 00:03:10,180 --> 00:03:13,870 that required that data to be there because it's a page 66 00:03:13,870 --> 00:03:16,543 that required the user to be authenticated. 67 00:03:17,420 --> 00:03:20,120 Here I'm redirecting to the starting page, 68 00:03:20,120 --> 00:03:21,540 which doesn't care about 69 00:03:21,540 --> 00:03:24,100 whether the user is authenticated or not, 70 00:03:24,100 --> 00:03:25,250 and therefore here, 71 00:03:25,250 --> 00:03:28,520 we can rely on the auto-saving mechanism, 72 00:03:28,520 --> 00:03:31,320 which has built into the express session package 73 00:03:31,320 --> 00:03:32,560 because we don't care 74 00:03:32,560 --> 00:03:35,560 whether redirecting or saving finishes first, 75 00:03:35,560 --> 00:03:39,453 since the redirected page doesn't rely on the saved data. 76 00:03:40,810 --> 00:03:43,670 So therefore now with that, if we save this, 77 00:03:43,670 --> 00:03:46,660 if we go back to the page, at the moment, 78 00:03:46,660 --> 00:03:49,520 I can still visit The Admin Page, 79 00:03:49,520 --> 00:03:51,940 but if I now click Logout, 80 00:03:51,940 --> 00:03:53,930 I'm redirected to the starting page. 81 00:03:53,930 --> 00:03:56,240 And if I now try to visit Admin, 82 00:03:56,240 --> 00:03:58,343 I get the Not authenticated page again. 83 00:03:59,380 --> 00:04:01,510 Now, if we have a look at the developer tools, 84 00:04:01,510 --> 00:04:03,530 I still have my session cookie, 85 00:04:03,530 --> 00:04:06,443 because again, I did not delete the session, 86 00:04:07,460 --> 00:04:10,470 but we'll see a difference in the database. 87 00:04:10,470 --> 00:04:14,680 If I query my sessions collection again, 88 00:04:14,680 --> 00:04:17,269 then we see the session is still there, 89 00:04:17,269 --> 00:04:20,673 but user is null and isAuthenticated is false. 90 00:04:21,899 --> 00:04:23,780 And that is the key thing. 91 00:04:23,780 --> 00:04:25,730 We still have our tickets, so to say, 92 00:04:25,730 --> 00:04:29,277 but it's now saying, "You don't get access. Sorry." 93 00:04:30,190 --> 00:04:31,390 This is what we did now, 94 00:04:31,390 --> 00:04:34,293 and that's how we can add this logout functionality.