1 00:00:01,170 --> 00:00:02,830 ‫Now, in order to set the stage 2 00:00:02,830 --> 00:00:04,710 ‫for the next couple of lectures, 3 00:00:04,710 --> 00:00:08,083 ‫let's start by learning a bit about Node architecture. 4 00:00:09,430 --> 00:00:11,980 ‫So let's represent that architecture here 5 00:00:11,980 --> 00:00:14,610 ‫in terms of Node's dependencies, 6 00:00:14,610 --> 00:00:16,620 ‫which are just a couple of libraries 7 00:00:16,620 --> 00:00:20,300 ‫that Node depends on in order to work properly. 8 00:00:20,300 --> 00:00:23,320 ‫So the Node run time has several dependencies, 9 00:00:23,320 --> 00:00:25,010 ‫and the most important ones are 10 00:00:25,010 --> 00:00:29,030 ‫the V8 (mumbles) engine and libuv. 11 00:00:29,030 --> 00:00:32,800 ‫Now we said before that Node is a JavaScript run time 12 00:00:32,800 --> 00:00:35,570 ‫based on Google's V8 engine, right? 13 00:00:35,570 --> 00:00:39,140 ‫And so, that is why it appears here as a dependency. 14 00:00:39,140 --> 00:00:42,620 ‫If it wasn't for V8, Node would have absolutely no 15 00:00:42,620 --> 00:00:45,980 ‫way of understanding the JavaScript code that we write. 16 00:00:45,980 --> 00:00:48,770 ‫And therefore, V8 is a fundamental part 17 00:00:48,770 --> 00:00:50,880 ‫in the Node architecture. 18 00:00:50,880 --> 00:00:55,450 ‫So again, the V8 engine is what converts JavaScript code 19 00:00:55,450 --> 00:00:59,470 ‫into machine code that a computer can actually understand. 20 00:00:59,470 --> 00:01:03,370 ‫Okay, but that alone is not enough to create a whole 21 00:01:03,370 --> 00:01:05,380 ‫server side framework like Node. 22 00:01:05,380 --> 00:01:09,100 ‫And so that is why we also have libuv in Node. 23 00:01:09,100 --> 00:01:12,380 ‫And libuv is an open source library with a 24 00:01:12,380 --> 00:01:15,060 ‫strong focus on asynchronous IO. 25 00:01:15,060 --> 00:01:16,860 ‫So, input output. 26 00:01:16,860 --> 00:01:19,500 ‫This layer is what gives Node access to the 27 00:01:19,500 --> 00:01:21,790 ‫underlying computer operating system, 28 00:01:21,790 --> 00:01:25,240 ‫file system, networking, and more. 29 00:01:25,240 --> 00:01:28,440 ‫Besides that, libuv also implements two extremely 30 00:01:28,440 --> 00:01:30,540 ‫important features of Node.JS 31 00:01:30,540 --> 00:01:34,010 ‫which are the event loop and also the thread pool. 32 00:01:34,010 --> 00:01:37,130 ‫And in simple terms, the event loop is responsible 33 00:01:37,130 --> 00:01:40,430 ‫for handling easy tasks like executing call backs 34 00:01:40,430 --> 00:01:44,790 ‫and network IO while the thread pool is for more heavy work 35 00:01:44,790 --> 00:01:48,200 ‫like file access or compression or something like that. 36 00:01:48,200 --> 00:01:50,120 ‫But you'll learn all about that, 37 00:01:50,120 --> 00:01:52,430 ‫so about the event loop and the thread pool, 38 00:01:52,430 --> 00:01:54,430 ‫in the next couple of videos. 39 00:01:54,430 --> 00:01:56,080 ‫One important thing to note here 40 00:01:56,080 --> 00:01:59,010 ‫is that libuv is actually completely written 41 00:01:59,010 --> 00:02:01,840 ‫in C++ and not in JavaScript. 42 00:02:01,840 --> 00:02:06,840 ‫And V8 itself, also uses C++ code besides JavaScript. 43 00:02:06,950 --> 00:02:10,150 ‫So therefore, Node itself is a program written 44 00:02:10,150 --> 00:02:14,170 ‫in C++ and JavaScript and not just in JavaScript 45 00:02:14,170 --> 00:02:16,530 ‫as you might expect, right? 46 00:02:16,530 --> 00:02:19,660 ‫Now the beauty of this is that Node.JS ties all 47 00:02:19,660 --> 00:02:22,310 ‫these libraries together, no matter if written 48 00:02:22,310 --> 00:02:25,640 ‫in C++ or JavaScript and then gives us 49 00:02:25,640 --> 00:02:30,380 ‫developers access to their functions in pure JavaScript. 50 00:02:30,380 --> 00:02:33,090 ‫So it really provides us with a very nice layer 51 00:02:33,090 --> 00:02:37,290 ‫of abstraction in order to make our lives a lot easier 52 00:02:37,290 --> 00:02:41,200 ‫instead of us like having to mess with C++ code. 53 00:02:41,200 --> 00:02:43,970 ‫That would be a terrible experience, right? 54 00:02:43,970 --> 00:02:47,450 ‫So again, this architecture allows us to write 55 00:02:47,450 --> 00:02:49,490 ‫100 percent pure JavaScript code, 56 00:02:49,490 --> 00:02:52,960 ‫running in Node.JS and still access functions like 57 00:02:52,960 --> 00:02:55,490 ‫for file reading, which behind the scenes are 58 00:02:55,490 --> 00:02:57,650 ‫actually implemented in libuv or 59 00:02:57,650 --> 00:03:01,290 ‫other libraries in the C++ language. 60 00:03:01,290 --> 00:03:03,090 ‫And speaking of other libraries, 61 00:03:03,090 --> 00:03:06,750 ‫Node does actually not only rely on V8 and libuv, 62 00:03:06,750 --> 00:03:10,920 ‫but also on http-parser for parsing http, 63 00:03:10,920 --> 00:03:15,920 ‫c-ares or something like that for some DNS request stuff, 64 00:03:16,420 --> 00:03:21,420 ‫OpenSSL for keptography, and also zlib for compression. 65 00:03:21,490 --> 00:03:24,740 ‫And these are not that important to understand, alright? 66 00:03:24,740 --> 00:03:27,830 ‫So in the end, when we have all these pieces nicely 67 00:03:27,830 --> 00:03:32,030 ‫fit together, we end up with Node.JS ready to be used 68 00:03:32,030 --> 00:03:35,000 ‫on the server side all four applications. 69 00:03:35,000 --> 00:03:37,670 ‫And next up, you will learn more about threads 70 00:03:37,670 --> 00:03:39,600 ‫in Node and the thread pool. 71 00:03:39,600 --> 00:03:41,663 ‫So stay tuned for that one.