1 00:00:02,110 --> 00:00:05,110 Now just as with MySQL and NodeJS 2 00:00:05,110 --> 00:00:08,590 in order to connect to the MongoDB database 3 00:00:08,590 --> 00:00:10,350 from inside our NodeJS code, 4 00:00:10,350 --> 00:00:12,670 we wanna use a third-party package, 5 00:00:12,670 --> 00:00:15,640 so that we don't need to manage the technical details 6 00:00:15,640 --> 00:00:19,820 of establishing and holding such a connection on our own. 7 00:00:19,820 --> 00:00:22,880 And for this you can search for NodeJS MongoDB, 8 00:00:22,880 --> 00:00:26,650 and you'll find your official MongoDB Node Driver. 9 00:00:26,650 --> 00:00:29,520 So a package created by the MongoDB team, 10 00:00:29,520 --> 00:00:32,130 which is meant for exactly this use case 11 00:00:32,130 --> 00:00:35,943 that you wanna connect to MongoDB from inside NodeJS. 12 00:00:37,740 --> 00:00:39,990 Now, if you'd click on Quick Start there, 13 00:00:39,990 --> 00:00:42,400 you'll learn how you can set up a project 14 00:00:42,400 --> 00:00:46,040 and how you can install this MongoDB driver. 15 00:00:46,040 --> 00:00:47,573 It's this simple command. 16 00:00:48,440 --> 00:00:50,120 So we can copy this command. 17 00:00:50,120 --> 00:00:53,340 And then quit does running nodemon server here 18 00:00:53,340 --> 00:00:54,240 for the moment, 19 00:00:54,240 --> 00:00:57,210 and then run npm install mongodb 20 00:00:57,210 --> 00:00:59,690 to install this third-party package, 21 00:00:59,690 --> 00:01:02,690 which therefore was also added as a dependency 22 00:01:02,690 --> 00:01:04,653 to the package.json file. 23 00:01:05,598 --> 00:01:09,083 And then we can restart our node server. 24 00:01:10,214 --> 00:01:13,260 Now this alone, of course doesn't connect to the database, 25 00:01:13,260 --> 00:01:16,990 it just gives us a package that helps with the connection. 26 00:01:16,990 --> 00:01:18,170 And to manage the connection, 27 00:01:18,170 --> 00:01:21,950 I'll create a new folder in this project, 28 00:01:21,950 --> 00:01:25,623 the data folder with a database.js file. 29 00:01:26,460 --> 00:01:28,740 And in there, I wanna manage that connection 30 00:01:28,740 --> 00:01:30,590 so that in the other files 31 00:01:30,590 --> 00:01:32,790 where I wanna use that connection, 32 00:01:32,790 --> 00:01:35,330 I can just reach out to the single file. 33 00:01:35,330 --> 00:01:38,070 And I don't have to establish a new connection 34 00:01:38,070 --> 00:01:41,683 in every file where I wanna work with the database. 35 00:01:43,394 --> 00:01:45,920 Now, there are various ways of implementing 36 00:01:45,920 --> 00:01:48,900 such a connection and of managing such a connection, 37 00:01:48,900 --> 00:01:52,210 but here's a very common pattern which you can use 38 00:01:52,210 --> 00:01:55,280 in such a global database management file like this 39 00:01:55,280 --> 00:01:57,410 when working with MongoDB. 40 00:01:57,410 --> 00:02:01,610 We first start by importing this MongoDB package, 41 00:02:01,610 --> 00:02:03,600 which we just installed. 42 00:02:03,600 --> 00:02:06,270 By requiring mongodb like this 43 00:02:06,270 --> 00:02:08,652 in this database.js file here. 44 00:02:10,190 --> 00:02:15,190 Then as a next step, we can get the Mongo client 45 00:02:15,250 --> 00:02:18,563 by accessing mongodb.MongoClient. 46 00:02:19,667 --> 00:02:23,635 That's the actual thing that we need from the package 47 00:02:23,635 --> 00:02:25,802 to establish a connection. 48 00:02:27,295 --> 00:02:30,420 Now, this Mongo client can be used 49 00:02:30,420 --> 00:02:33,530 to call the connect method to then 50 00:02:33,530 --> 00:02:35,930 do exactly what the name suggests, 51 00:02:35,930 --> 00:02:39,230 to create a connection to a MongoDB server. 52 00:02:39,230 --> 00:02:40,810 So in this case to the server, 53 00:02:40,810 --> 00:02:43,093 which is running locally on our machine. 54 00:02:44,850 --> 00:02:48,260 So here we can call connect. 55 00:02:48,260 --> 00:02:50,100 And connect needs some information 56 00:02:50,100 --> 00:02:52,773 on how to establish this connection. 57 00:02:53,710 --> 00:02:56,480 Therefore we can pass and parameter values. 58 00:02:56,480 --> 00:02:59,560 And the first parameter value which we can pass 59 00:02:59,560 --> 00:03:03,493 is a URL that points to the MongoDB server. 60 00:03:04,800 --> 00:03:07,960 Now the format of this URL might look a bit weird, 61 00:03:07,960 --> 00:03:09,650 but it is a format understood 62 00:03:09,650 --> 00:03:12,120 by this third-party package here. 63 00:03:12,120 --> 00:03:17,080 It looks like this, you type mongodb:// 64 00:03:17,080 --> 00:03:21,280 and then localhost:27017, 65 00:03:21,280 --> 00:03:23,480 since that is the address that will be used 66 00:03:23,480 --> 00:03:27,113 by that MongoDB server on our local system. 67 00:03:28,850 --> 00:03:31,140 Now, you know this from the official docs. 68 00:03:31,140 --> 00:03:32,870 For example, if you look at them 69 00:03:32,870 --> 00:03:35,363 or of course by simply believing me here. 70 00:03:36,500 --> 00:03:38,190 This year might look a bit strange, 71 00:03:38,190 --> 00:03:40,760 but it's simply telling the MongoDB driver 72 00:03:40,760 --> 00:03:43,520 that it should connect to this server 73 00:03:43,520 --> 00:03:46,190 with a special protocol, so to say. 74 00:03:46,190 --> 00:03:48,130 Which are some low level details 75 00:03:48,130 --> 00:03:50,030 we don't have to worry about. 76 00:03:50,030 --> 00:03:52,300 In the end, this will be the URL pointing 77 00:03:52,300 --> 00:03:55,290 to our locally running MongoDB server. 78 00:03:55,290 --> 00:03:57,320 That's the port number that's being used 79 00:03:57,320 --> 00:03:59,900 by that server out of the box by default. 80 00:03:59,900 --> 00:04:03,353 And therefore, this should establish such a connection. 81 00:04:04,640 --> 00:04:09,190 You'll also find this here in the official documentation. 82 00:04:09,190 --> 00:04:12,760 If you have a look at their example, 83 00:04:12,760 --> 00:04:16,040 they are using a slightly different URL here 84 00:04:16,040 --> 00:04:18,490 because they are connecting to a cluster. 85 00:04:18,490 --> 00:04:21,079 But if you have a look at connect to localhost, 86 00:04:21,079 --> 00:04:23,760 you see exactly this address I showed you 87 00:04:23,760 --> 00:04:25,223 a couple of seconds ago. 88 00:04:26,120 --> 00:04:30,030 So that's how we can connect to our MongoDB server here. 89 00:04:30,030 --> 00:04:32,800 We'll come back to connecting to such a cluster here 90 00:04:32,800 --> 00:04:35,940 later in the course, once we talk about deployment 91 00:04:35,940 --> 00:04:39,920 and about running a database for a real website, 92 00:04:39,920 --> 00:04:42,530 that's being exposed to users. 93 00:04:42,530 --> 00:04:45,130 But for development, this local host solution 94 00:04:45,130 --> 00:04:46,533 is absolutely fine. 95 00:04:47,870 --> 00:04:50,720 Now this would establish such a connection, 96 00:04:50,720 --> 00:04:53,590 and it actually establishes such a connection 97 00:04:53,590 --> 00:04:56,490 by returning a so-called promise. 98 00:04:56,490 --> 00:04:59,834 And we learned about promises in this more advanced 99 00:04:59,834 --> 00:05:03,370 JavaScript course section a couple of hours ago. 100 00:05:03,370 --> 00:05:06,070 And we also already used promises 101 00:05:06,070 --> 00:05:08,510 when we worked with MySQL. 102 00:05:08,510 --> 00:05:11,280 So I'm not going to explain them in depth here, 103 00:05:11,280 --> 00:05:14,430 instead of check out those earlier course sections 104 00:05:14,430 --> 00:05:17,240 to understand what promises are. 105 00:05:17,240 --> 00:05:18,780 In the end, promises allow us 106 00:05:18,780 --> 00:05:21,130 to work with asynchronous code. 107 00:05:21,130 --> 00:05:23,580 So code that can take a little bit longer 108 00:05:23,580 --> 00:05:25,410 to execute, so to say. 109 00:05:25,410 --> 00:05:27,450 And here establishing such a connection 110 00:05:27,450 --> 00:05:29,010 can take a bit longer, 111 00:05:29,010 --> 00:05:32,383 therefore this is actually returning such a promise. 112 00:05:33,550 --> 00:05:35,570 And therefore what I'll actually do here 113 00:05:35,570 --> 00:05:37,350 is I'll create a new function. 114 00:05:37,350 --> 00:05:39,810 Connect could be the name. 115 00:05:39,810 --> 00:05:42,890 And I'll turn this into an async function 116 00:05:42,890 --> 00:05:44,553 with the async keyword, 117 00:05:45,650 --> 00:05:48,620 and then move this line of code into this function, 118 00:05:48,620 --> 00:05:50,810 and then use the await keyword 119 00:05:50,810 --> 00:05:54,060 to wait for this operation to finish. 120 00:05:54,060 --> 00:05:56,670 And then when using does await keyword, 121 00:05:56,670 --> 00:06:00,200 this will eventually give us the database client, 122 00:06:00,200 --> 00:06:01,340 which we now have. 123 00:06:01,340 --> 00:06:04,683 So which now gives us access to the connected database. 124 00:06:06,010 --> 00:06:08,460 So now whenever we call the connect function 125 00:06:08,460 --> 00:06:11,570 from anywhere in our code, which we're not doing yet, 126 00:06:11,570 --> 00:06:13,220 but which we will do soon, 127 00:06:13,220 --> 00:06:16,533 will establish such a connection and get such a client. 128 00:06:19,120 --> 00:06:21,040 Now, as a side note, this connection, 129 00:06:21,040 --> 00:06:22,350 which is established here, 130 00:06:22,350 --> 00:06:25,750 will actually automatically be a connection pool, 131 00:06:25,750 --> 00:06:28,860 which is managed by the MongoDB package. 132 00:06:28,860 --> 00:06:31,650 So multiple connections will be established. 133 00:06:31,650 --> 00:06:34,280 And whenever you then need to run a query, 134 00:06:34,280 --> 00:06:36,770 you will automatically get an open connection, 135 00:06:36,770 --> 00:06:37,870 which you can use. 136 00:06:37,870 --> 00:06:40,810 And the MongoDB package will manage 137 00:06:40,810 --> 00:06:44,210 all those connections for us, which is very convenient. 138 00:06:44,210 --> 00:06:46,203 So we don't have to worry about that. 139 00:06:47,920 --> 00:06:49,330 Hence, we get this client, 140 00:06:49,330 --> 00:06:51,340 which would allow us to interact 141 00:06:51,340 --> 00:06:53,330 with the connected database, 142 00:06:53,330 --> 00:06:56,870 but I don't wanna run my queries and commands 143 00:06:56,870 --> 00:06:58,270 from inside this file. 144 00:06:58,270 --> 00:07:02,160 I wanna run those commands from inside another file. 145 00:07:02,160 --> 00:07:03,790 And therefore what I'll do here 146 00:07:03,790 --> 00:07:05,500 is I'll add a new variable. 147 00:07:05,500 --> 00:07:07,830 Database, could be the name. 148 00:07:07,830 --> 00:07:12,830 And actually I will set database equal to client.db here. 149 00:07:15,850 --> 00:07:18,700 And db is a method that we can execute 150 00:07:18,700 --> 00:07:22,140 to connect to a specific database on the server 151 00:07:22,990 --> 00:07:25,240 because here we only establish a connection 152 00:07:25,240 --> 00:07:27,080 to the server as a whole. 153 00:07:27,080 --> 00:07:30,440 Now we can call the db method to actually talk 154 00:07:30,440 --> 00:07:33,880 to the blog database on that server. 155 00:07:33,880 --> 00:07:36,330 And that is the database we worked with 156 00:07:36,330 --> 00:07:38,873 a couple of minutes ago in the MongoDB shell. 157 00:07:40,090 --> 00:07:44,408 And the result of calling db is an access to exactly 158 00:07:44,408 --> 00:07:47,750 that database on the MongoDB server 159 00:07:47,750 --> 00:07:50,790 and that stands for what I store in this database variable, 160 00:07:50,790 --> 00:07:52,660 which is deliberately created 161 00:07:52,660 --> 00:07:54,510 outside of this connect function 162 00:07:54,510 --> 00:07:57,000 so that it can be used in this whole file, 163 00:07:57,000 --> 00:07:59,563 and not just in this connect function. 164 00:08:00,760 --> 00:08:03,580 Because my goal is to make this variable 165 00:08:03,580 --> 00:08:06,143 available outside of this file as well now. 166 00:08:07,800 --> 00:08:10,977 Simply by adding another function, 167 00:08:10,977 --> 00:08:13,810 getDb could be the name 168 00:08:13,810 --> 00:08:16,733 where I simply return database, 169 00:08:17,780 --> 00:08:18,683 like this. 170 00:08:20,157 --> 00:08:24,660 And we could even check if databases may be not set 171 00:08:24,660 --> 00:08:26,720 if it's falsey, 172 00:08:26,720 --> 00:08:30,030 and if that's the case, we could throw an error 173 00:08:30,030 --> 00:08:35,030 where we say "Database connection not established!" 174 00:08:35,789 --> 00:08:38,270 Just to ensure that we're not trying to work 175 00:08:38,270 --> 00:08:41,750 with that database before we actually have it. 176 00:08:41,750 --> 00:08:43,669 So that connect must've been called 177 00:08:43,669 --> 00:08:46,470 before we try to use the database. 178 00:08:46,470 --> 00:08:49,270 That's a little security check for ourselves, 179 00:08:49,270 --> 00:08:50,830 which we can add here. 180 00:08:50,830 --> 00:08:54,493 It's not mandatory, but also not a bad idea. 181 00:08:56,340 --> 00:08:58,570 And now as a last step here, 182 00:08:58,570 --> 00:09:02,830 I will add the module.exports statement 183 00:09:02,830 --> 00:09:05,830 and export an object here. 184 00:09:05,830 --> 00:09:07,590 And that will be an object 185 00:09:07,590 --> 00:09:12,590 where I expose both these functions to the outside world. 186 00:09:14,110 --> 00:09:18,570 So I'll add connectToDatabase as a key here 187 00:09:18,570 --> 00:09:22,110 and point at the connect function like this. 188 00:09:22,110 --> 00:09:25,670 And then as a second property in this exported object, 189 00:09:25,670 --> 00:09:28,673 I'll add getDb as a key and point at getDb. 190 00:09:30,691 --> 00:09:32,740 So the things on the right side of the colons 191 00:09:32,740 --> 00:09:36,290 are these function names we have here in this file. 192 00:09:36,290 --> 00:09:40,010 And by just pointing at them and not executing them, 193 00:09:40,010 --> 00:09:42,100 so by not adding parentheses, 194 00:09:42,100 --> 00:09:44,920 we make sure that they are not executed yet, 195 00:09:44,920 --> 00:09:48,330 but that instead they can be executed in our files, 196 00:09:48,330 --> 00:09:50,520 which import this file, 197 00:09:50,520 --> 00:09:53,310 which is exactly what I wanna achieve. 198 00:09:53,310 --> 00:09:56,160 This file should just be a utility file. 199 00:09:56,160 --> 00:09:58,470 The functions should actually be executed 200 00:09:58,470 --> 00:10:00,513 from somewhere else in our code. 201 00:10:02,360 --> 00:10:05,920 And then for now with this file added here, 202 00:10:05,920 --> 00:10:08,400 we can go back to another place 203 00:10:08,400 --> 00:10:11,283 where I do wanna establish this connection. 204 00:10:12,220 --> 00:10:15,310 And what could be a good place for doing that? 205 00:10:15,310 --> 00:10:18,480 Well, actually it would be app.js, 206 00:10:18,480 --> 00:10:22,870 where we start this overall node-express server 207 00:10:22,870 --> 00:10:25,650 and where we initialize all our settings 208 00:10:25,650 --> 00:10:29,010 and all our middlewares, that's a great place 209 00:10:29,010 --> 00:10:31,863 for actually also connecting to the database. 210 00:10:32,840 --> 00:10:35,440 And I wanna connect to the database here, 211 00:10:35,440 --> 00:10:37,680 once all the other set up was done. 212 00:10:37,680 --> 00:10:39,220 So here at the bottom, maybe. 213 00:10:39,220 --> 00:10:41,730 There, I wanna connect to my database. 214 00:10:41,730 --> 00:10:45,160 And actually I only wanna start listening here 215 00:10:45,160 --> 00:10:50,160 on port 3000 if that database connection was established. 216 00:10:51,750 --> 00:10:54,200 And to ensure that this is the case, 217 00:10:54,200 --> 00:10:57,270 I'll import my database, 218 00:10:57,270 --> 00:11:00,430 or my db file 219 00:11:00,430 --> 00:11:05,430 by requiring ./data/database like this, 220 00:11:07,170 --> 00:11:11,743 that will actually require this database file. 221 00:11:12,970 --> 00:11:17,870 And then with that here, we can call connectToDatabase, 222 00:11:17,870 --> 00:11:20,390 this one function we're exporting. 223 00:11:20,390 --> 00:11:23,960 And that will then return a promise. 224 00:11:23,960 --> 00:11:28,100 And here we can't necessarily use await, 225 00:11:28,100 --> 00:11:30,913 since we're not inside of an async function here. 226 00:11:32,060 --> 00:11:34,960 Hence, what we can do here is we can use the then method, 227 00:11:34,960 --> 00:11:38,290 which you also learned about in an earlier course section, 228 00:11:38,290 --> 00:11:40,040 which takes a function, 229 00:11:40,040 --> 00:11:42,610 in this case, for example, an anonymous function 230 00:11:42,610 --> 00:11:45,680 that will be executed once this promise resolved, 231 00:11:45,680 --> 00:11:47,393 so once this promise is done. 232 00:11:48,360 --> 00:11:52,460 And then I'll move app.listen inside of this function, 233 00:11:52,460 --> 00:11:55,960 so that app.listen 3000 only executed 234 00:11:55,960 --> 00:11:59,440 once the database connection was established. 235 00:11:59,440 --> 00:12:03,240 Simply to ensure that we only start this web server, 236 00:12:03,240 --> 00:12:05,673 if we have an active database connection. 237 00:12:07,860 --> 00:12:11,920 Now we could also handle the connection in different cases. 238 00:12:11,920 --> 00:12:13,710 We could establish it differently, 239 00:12:13,710 --> 00:12:17,050 and we could also, for example, check if the server crashes 240 00:12:17,050 --> 00:12:18,340 or anything like that. 241 00:12:18,340 --> 00:12:22,520 And in that case, shut down our database connection, 242 00:12:22,520 --> 00:12:25,450 but I don't wanna make things too complex here. 243 00:12:25,450 --> 00:12:27,310 And therefore, for the moment, 244 00:12:27,310 --> 00:12:29,860 I'll stop my running nodemon server 245 00:12:29,860 --> 00:12:32,630 by pressing control + C in this terminal, 246 00:12:32,630 --> 00:12:35,020 and I'll save all files 247 00:12:35,020 --> 00:12:38,100 and then restart this all with npm start. 248 00:12:38,100 --> 00:12:40,420 And since it now is running again, 249 00:12:40,420 --> 00:12:43,780 and I can visit my blog again, 250 00:12:43,780 --> 00:12:45,790 it looks like everything works. 251 00:12:45,790 --> 00:12:47,700 And it looks like indeed we do have 252 00:12:47,700 --> 00:12:49,453 this active connection now. 253 00:12:50,970 --> 00:12:53,270 And therefore, now we established a connection 254 00:12:53,270 --> 00:12:54,560 as a next step. 255 00:12:54,560 --> 00:12:58,210 We can now make sure that we actually query our authors 256 00:12:58,210 --> 00:13:01,010 so that we can pre-populate this dropdown 257 00:13:01,010 --> 00:13:04,643 on the create post page with the author's data.