WEBVTT 1 00:00:00.188 --> 00:00:04.190 Let's start a section with a general overview 2 00:00:04.190 --> 00:00:06.750 of Modern JavaScript Development. 3 00:00:06.750 --> 00:00:10.760 So basically of how we write JavaScript today. 4 00:00:10.760 --> 00:00:13.230 Because when we built applications, 5 00:00:13.230 --> 00:00:17.350 we don't just write all of our code into one big script 6 00:00:17.350 --> 00:00:20.780 send that script as it is to the browser, 7 00:00:20.780 --> 00:00:22.590 and call it a day. 8 00:00:22.590 --> 00:00:24.640 Now it used to be like this, 9 00:00:24.640 --> 00:00:27.360 but the way we built JavaScript applications, 10 00:00:27.360 --> 00:00:31.373 has changed tremendously over the last couple of years. 11 00:00:32.940 --> 00:00:34.650 So back in the day, 12 00:00:34.650 --> 00:00:36.480 we used to write all our codes 13 00:00:36.480 --> 00:00:40.720 into one big script or maybe multiple scripts. 14 00:00:40.720 --> 00:00:45.190 But today, we divide our projects into multiple modules 15 00:00:45.190 --> 00:00:48.210 and these modules can share data between them 16 00:00:48.210 --> 00:00:52.240 and make our code more organized and maintainable. 17 00:00:52.240 --> 00:00:54.930 Now, one great thing about modules 18 00:00:54.930 --> 00:00:58.160 is that we can also include 3rd-party modules 19 00:00:58.160 --> 00:01:00.100 into our own code. 20 00:01:00.100 --> 00:01:03.500 And there are thousands of open source modules, 21 00:01:03.500 --> 00:01:05.630 which we also call packages, 22 00:01:05.630 --> 00:01:09.590 that developers share on the NPM repository. 23 00:01:09.590 --> 00:01:14.120 And we can then use these packages for free in our own code. 24 00:01:14.120 --> 00:01:18.520 For example, the popular React framework or jQuery, 25 00:01:18.520 --> 00:01:20.840 or even the Leaflet library, 26 00:01:20.840 --> 00:01:24.210 that we used before in our Mapty project. 27 00:01:24.210 --> 00:01:27.523 All of these packages are available through NPM. 28 00:01:28.380 --> 00:01:31.920 Now NPM stands for Node Package Manager, 29 00:01:31.920 --> 00:01:35.030 because it was originally developed together 30 00:01:35.030 --> 00:01:38.650 with Node.js and 4Node.js. 31 00:01:38.650 --> 00:01:41.550 However, NPM has established itself 32 00:01:41.550 --> 00:01:43.560 as the go to repository 33 00:01:43.560 --> 00:01:45.520 for all kinds of packages 34 00:01:45.520 --> 00:01:48.210 in Modern JavaScript Development. 35 00:01:48.210 --> 00:01:50.810 Now, in order to actually download 36 00:01:50.810 --> 00:01:53.660 and use and share packages, 37 00:01:53.660 --> 00:01:58.050 we use the NPM software installed on our computer. 38 00:01:58.050 --> 00:02:01.220 And this is just a simple command line interface 39 00:02:01.220 --> 00:02:03.970 that allows us to do all that. 40 00:02:03.970 --> 00:02:07.570 So basically NPM is both the repository 41 00:02:07.570 --> 00:02:10.910 in which packages live and a program that we use 42 00:02:10.910 --> 00:02:15.910 on our computers to install and manage these packages. 43 00:02:16.010 --> 00:02:20.470 So let's say that we are done writing our project code. 44 00:02:20.470 --> 00:02:23.340 So we divided it into multiple modules 45 00:02:23.340 --> 00:02:26.900 and we included some 3rd-party modules as well. 46 00:02:26.900 --> 00:02:30.650 And so now the development step is complete. 47 00:02:30.650 --> 00:02:34.790 However, usually that's not the end of the story. 48 00:02:34.790 --> 00:02:38.890 At least not when rebuilding a real world application. 49 00:02:38.890 --> 00:02:41.120 Instead, our project now needs 50 00:02:41.120 --> 00:02:43.260 to go through a build process, 51 00:02:43.260 --> 00:02:47.590 where one big final JavaScript bundle is built. 52 00:02:47.590 --> 00:02:49.420 And that's the final file, 53 00:02:49.420 --> 00:02:53.190 which we will deploy to our web server for production. 54 00:02:53.190 --> 00:02:55.970 So basically it's the JavaScript file, 55 00:02:55.970 --> 00:02:59.610 that will be sent to browsers in production. 56 00:02:59.610 --> 00:03:02.350 And production simply means that the application 57 00:03:02.350 --> 00:03:06.740 is being used by real users in the real world. 58 00:03:06.740 --> 00:03:10.520 Now, a build process can be something really complex, 59 00:03:10.520 --> 00:03:12.390 but we gonna keep it simple here 60 00:03:12.390 --> 00:03:14.830 and only include two steps. 61 00:03:14.830 --> 00:03:17.680 And the first step, we'll bundle all our modules 62 00:03:17.680 --> 00:03:20.390 together into one big file. 63 00:03:20.390 --> 00:03:22.660 This is a pretty complex process 64 00:03:22.660 --> 00:03:25.210 which can eliminate unused code 65 00:03:25.210 --> 00:03:27.453 and compress or code as well. 66 00:03:28.350 --> 00:03:32.790 Now this step is super important for two big reasons. 67 00:03:32.790 --> 00:03:36.750 First, older browsers don't support modules at all. 68 00:03:36.750 --> 00:03:40.300 And so code that's in a module could not be executed 69 00:03:40.300 --> 00:03:42.560 by any older browser. 70 00:03:42.560 --> 00:03:45.720 And second, it's also better for performance 71 00:03:45.720 --> 00:03:48.160 to send less files to the browser, 72 00:03:48.160 --> 00:03:49.950 and it's also beneficial that 73 00:03:49.950 --> 00:03:53.140 the bundling step compresses our code. 74 00:03:53.140 --> 00:03:55.460 But anyway, as the second step, 75 00:03:55.460 --> 00:03:59.100 we do something called transpiling and polyfilling, 76 00:03:59.100 --> 00:04:00.940 which is basically to convert 77 00:04:00.940 --> 00:04:02.890 all modern JavaScript syntax 78 00:04:02.890 --> 00:04:06.560 and features back to old ES5 syntax, 79 00:04:06.560 --> 00:04:09.200 so that even older browsers can understand 80 00:04:09.200 --> 00:04:11.470 our code without breaking. 81 00:04:11.470 --> 00:04:16.080 And this is usually done using a tool called Babel. 82 00:04:16.080 --> 00:04:18.910 So, remember that I said right in the beginning 83 00:04:18.910 --> 00:04:21.620 of the course, that we were gonna do this, 84 00:04:21.620 --> 00:04:25.090 and in this section, we will finally do it. 85 00:04:25.090 --> 00:04:29.090 So these are the two steps of our build process, 86 00:04:29.090 --> 00:04:31.030 and after these two steps, 87 00:04:31.030 --> 00:04:33.940 we end up with that final JavaScript bundle, 88 00:04:33.940 --> 00:04:37.920 ready to be deployed on a server for production. 89 00:04:37.920 --> 00:04:41.920 Now, of course we don't perform these steps ourselves. 90 00:04:41.920 --> 00:04:45.070 Instead, we use a special tool to implement 91 00:04:45.070 --> 00:04:47.080 this build process for us. 92 00:04:47.080 --> 00:04:49.600 And the most common build tools available, 93 00:04:49.600 --> 00:04:52.910 are probably webpack and Parcel. 94 00:04:52.910 --> 00:04:55.590 And these are called JavaScript bundlers 95 00:04:55.590 --> 00:05:00.550 because well, as the name says they take our raw code 96 00:05:00.550 --> 00:05:04.110 and transform it into a JavaScript bundle. 97 00:05:04.110 --> 00:05:06.860 Now Webpack is the more popular one, 98 00:05:06.860 --> 00:05:10.650 but it can be really hard and confusing to set it up. 99 00:05:10.650 --> 00:05:12.950 So that's because there's a lot of stuff 100 00:05:12.950 --> 00:05:14.950 that we need to configure manually, 101 00:05:14.950 --> 00:05:17.600 in order to make it work properly. 102 00:05:17.600 --> 00:05:21.990 Parcel, on the other hand is a zero configuration bundler, 103 00:05:21.990 --> 00:05:24.700 which simply works out of the box. 104 00:05:24.700 --> 00:05:26.010 And so in this bundler, 105 00:05:26.010 --> 00:05:28.700 we don't have to write any set up code, 106 00:05:28.700 --> 00:05:30.820 which is really amazing. 107 00:05:30.820 --> 00:05:33.980 So I personally absolutely love Parcel 108 00:05:33.980 --> 00:05:35.980 and I use it all the time, 109 00:05:35.980 --> 00:05:38.390 and I think that you will love it too. 110 00:05:38.390 --> 00:05:41.010 And so, that is the JavaScript bundler 111 00:05:41.010 --> 00:05:43.373 that we gonna use later in the section. 112 00:05:44.430 --> 00:05:46.910 Now these development tools are actually 113 00:05:46.910 --> 00:05:49.940 also available on NPM. 114 00:05:49.940 --> 00:05:53.530 So just like packages that we include in our code, 115 00:05:53.530 --> 00:05:57.960 we will download and manage tools using NPM as well. 116 00:05:57.960 --> 00:06:00.530 And these tools include the live-server 117 00:06:00.530 --> 00:06:02.770 that we've been using all along, 118 00:06:02.770 --> 00:06:05.790 the Parcel bundler that we just talked about 119 00:06:05.790 --> 00:06:09.163 or Babel to transpile code back to ES5. 120 00:06:10.230 --> 00:06:14.340 All right, so this is a high level overview, 121 00:06:14.340 --> 00:06:18.310 of how we develop Modern JavaScript applications today. 122 00:06:18.310 --> 00:06:22.240 And if you ask me, this is really exciting stuff, 123 00:06:22.240 --> 00:06:24.960 because this is how professional developers 124 00:06:24.960 --> 00:06:27.570 actually write JavaScript today. 125 00:06:27.570 --> 00:06:29.830 And so in the rest of the section, 126 00:06:29.830 --> 00:06:32.710 you will take a big step in the direction 127 00:06:32.710 --> 00:06:35.473 of becoming a professional developer too.