Marat BN — Marat Borisovich Nepomnyashy's home page

Introduction

Back in early 2017, I wrote a blog tutorial Step-by-Step Minimalistic React Web App with Just the Bare Essentials which is compatible with the legacy Webpack 1, but since then Webpack 1 has become obsolete, and so that tutorial has become obsolete as well. So I wrote another tutorial Step-by-Step Minimalistic React Web App with Webpack 3 and Just the Bare Essentials that is compatible with Webpack 3, which is now outdated / borderline obsolete since the introduction of Webpack 4 in February 2018. This new blog tutorial provides instructions on how to produce a minimalistic React app with the currently latest (June 2018) Webpack version 4.

Additional preliminary Information

Proper Webpack configuration is absolutely crucial to having a working React app, and the procedure and various dependencies differ slightly between the different versions of Webpack. Most of the steps for developing a React app with Webpack 4 are exactly the same as with Webpack 3, however, some specifics are different. I list these out in the Summary section. Also, just like the Webpack 3 tutorial, this tutorial has been developed on Ubuntu 18.04 with Node 8.10.0 and NPM 3.5.2.

Sections to read from the original tutorial

For anybody unfamiliar with React, I recommend that you first read the following sections from the original tutorial:

• The most confusing thing about React and the Facebook React documentation
• The most confusing thing about JSX
• Virtual DOM — The least confusing thing about React and what makes it so cool
• Why React has emerged as the dominant UI toolkit
• The most confusing thing about starting to build a React app

The philosophy and purpose behind React has not changed.

Setting up and working with Babel, Webpack 4, Node.js, and NPM

1. Install Node.js

   The Node.js is the runtime environment inside which all of our other tools will be running. So we need to natively install Node.js onto the operating system of the computer on which we’ll be doing our development. The official installation instructions for Node.js are here on their website.

   On my Ubuntu 18.04 test machine, I just did apt-get install nodejs with root permissions. This installed Node 8.10.0.

   So install Node.js as the first step of this tutorial. This has been documented in the example repo commit 0bd359af4b8e00b2b8bd52293a971b30b9dead81.

2. Make sure NPM is also installed

   The NPM Node Package Manager will be used to install Webpack 4 and Babel. On some OSes NPM also gets installed as a dependency of Node.js, but on my Ubuntu 18.04 test system this was not the case. I had to install it manually with apt-get install npm with root permissions. If you’re not on Ubuntu 18.04, please refer to the official installing NPM page. To verify that you have NPM installed, run npm -v inside your console. I’m personally currently running NPM version 3.5.2.

   This has been documented in the example repo commit 9c422cdc7a318f2b3236a5e7792ecfbd75ef3961.

3. Install Webpack 4

   The Webpack module bundler, specifically version 4 for this tutorial, will manage the whole build process for our app, (including running the Babel transpiler,) so we need to install it next. This time we’ll be installing with NPM rather than with the native OS package manager. In fact, from this point on, we’ll only be using NPM whenever we need to install any additional software. The NPM package for Webpack is webpack. Run the command: npm install webpack@^4.12.1 Notice the version specifier @^4.12.1 at the end. This specifier is crucial to insure that Webpack 4 is installed, and not 5 or some newer version when it gets released in the future. The specific version 4.12.1 is the very latest at the time this is written, but the ^ caret operator will allow this command to download newer versions as they are released, as long as the major version number still remains 4.

   This step is documented in the example repo commit bd72ca7155b3690f884fc5bbc265a567100e0bab.

4. Install separate package for Webpack CLI

   Webpack 4 needs a separate CLI package to be explicitly installed alongside it, or otherwise it will complain and hang until such a package is installed. This package can be webpack-cli. The command to install it is: npm install webpack-cli

   This step is documented in the example repo commit 59947b28605e763d21b748b3c7b302120b2f2d35.

5. Add node_modules to ‘.gitignore’

   At this point, a new directory node_modules/ will appear at the root of your project directory, and it will contain the logic for Webpack and all its dependencies. This directory and all its contents currently take up 114 MB on the Ubuntu 18.04 system I’m using. We don’t have to install Webpack inside our project, in fact, NPM allows installing all packages globally; however, for the purpose of this tutorial we’re installing all packages locally to get a better idea of what we need to install, and also not to mess with the global system configuration.

   However, even though we’re going to keep node_modules/ locally, we’re not going to keep track of its contents with our Git repository, or at least I’m not. So I recommend you create a .gitignore with node_modules/ in it. This is done in the example repo commit 2b201fb66fb3538667cc1cf9cc347e3bf623b3df.

6. Prepare JavaScript entry logic

   Now that we have Webpack 4 installed, we could immediately continue to installing Babel, but not just yet. First, we’re going to introduce some very basic Webpack 4 configuration without Babel, and then when we install Babel, we’re going to add the Babel-specific configuration on top of that initial configuration. This way we’ll get to see only the bare minimum of what Webpack can operate with, and what Babel requires.

   So Webpack is a module bundler. What that means is that it takes in several files (modules), and spits out a single file with all those modules combined. Actually the output does not always have to be a single file, but that’s what it will be for the purpose of this tutorial. We bundle several files into 1 to make the logic they contain faster for the browser to download.

   By convention, we will keep our Webpack input files in the subdirectory webpack_in, and our output file will be dumped by Webpack into webpack_out. Our primary input files will import secondary input files, but since Webpack will start the packing with the primary files, and that’s also where the JavaScript logic interpretor will start when our code is finally executed, we will call our primary files Webpack entry files.

   So by using this nomenclature, our initial entry file will be webpack_in/entry.js. For now, all the logic it will contain will be a console log to indicate that it has been interpreted when we test it in the browser. I have prepared this initial logic in the example repo commit 1c95d3148eccb7eb21e17b15ceb1be23bdc5b4ad.

7. Configure Webpack 4 to pack the JavaScript entry logic

   OK, so now we have our basic JavaScript entry file. Next, we must tell Webpack to grab it and spit-out webpack_out/minimalistic_react.js For now we’re processing just 1 file and outputting just 1 file, but that’s just for the sake of this tutorial, to allow us to see the most basic Webpack configuration. Pretty soon we’ll be processing a lot more input files than just one. The output file name minimalistic_react.js is just an arbitrary name I chose.

   We communicate our parameters to Webpack via a special configuration file, which we’re going to call webpack.config.js. As can be deduced by its file extension, the configuration file itself is a JavaScript file executed by the Node.js runtime environment. I have prepared this file in the example repo commit 0e1a6db3eba8960f87e93a7a7301298590222f77.

   As you can see, this time the configuration logic is 9 lines rather than 8 as for Webpack 1 and 3. As before, we import Node.js API path to be able to join directory names with the host OS directory separation token, next, we specify our entry file webpack_in/entry.js, and then specify our output to be webpack_out/minimalistic_react.js. But then, there’s this additional configuration with the field mode being set to development. This additional configuration specifies that for now we want to do an unminified development build for quicker testing and easier debugging. We did not need to specify this with versions 1 and 3, because they do development build by default, but with Webpack 4 there’s a major change in that it does the production build by default.

8. Generate initial JavaScript output with Webpack 4

   Time to run Webpack with our just-prepared config! This is done with the command: ./node_modules/webpack/bin/webpack.js --config ./webpack.config.js This step has been documented in the example repo commit 8b652108e57d0e471d098cff4af7d7a109bda6ff.

   From this point on it will be necessary to re-bundle our JavaScript again and again every time we change it. This is one drawback to building React-based applications. However, we can save ourselves the trouble of typing the Webpack console command each time by having Webpack “watch” our input files for changes, and re-bundle automatically when changes are detected. This is done by adding the --watch command line parameter. To use it, open a separate terminal window in the project directory, and enter the command: ./node_modules/webpack/bin/webpack.js --config ./webpack.config.js --watch I documented this in the commit 2ba57f4cae6b6ec779387b03421ee23d00373bef.

   The Webpack process will not exit, but will just sit there and wait for new changes. If you’ll be running Webpack in this mode, then make sure to periodically check its output for reports of any syntax errors you might accidentally introduce into your input code.

9. Add the generated JavaScript file to ‘.gitignore’

   Since we just generated our output JavaScript, we’re going to have a new file webpack_out/minimalistic_react.js. This file is currently 4628 bytes on my system, while the input file webpack_in/entry.js is only 282 bytes. If we open the generated file, we can see that Webpack added a whole bunch of additional lines denoted by commented-out asterisks. This is normal, and since right now we’re working with a development build it is not going to be a problem. Later on in this tutorial, after we actually implement our basic React app, we’re going to experiment with minified production builds, at which time we’ll add additional Webpack configuration to prevent this superfluous generated bloat.

   The generated output file is bulky and will keep changing everytime we make a change to our input files. So it makes sense to add it to .gitignore as well to keep our Git history clean. This step has been done in the example repo commit 4852c9853dc571bd58220dae1dee08e50832fe28.

10. Verify proper packing and interpretation of the JavaScript entry logic

    OK, so since now we have our generated JavaScript file, it’s time to test it with an HTML test page! I just added one with the example repo commit 9890a3ef52296104c8c650cb00476ac39cb97aea, and we can try it here.

    This page will not look like much, as it should because it does not have much, but if we open the browser web inspector and look inside the JavaScript Console tab, we will see that our test page just emitted the string “JavaScript entry logic.” to the console. That’s exactly what we want to see, as that indicates that the logic inside that entry JavaScript file from step 6 has been packed by Webpack into its generated output, picked-up by our test page, and interpreted by the browser. Our basic Webpack configuration and build infrastructure up to this point is working!

    The one crucial detail about this page is that it loads the generated JavaScript webpack_out/minimalistic_react.js not inside the <head> tag as is so common with using <script> tags, but at the very bottom of the <body> tag. There is an important reason for this — when we ultimately implement our React app, it will need to render itself into its root container element, We need to load our React JavaScript after the browser renders this root container element to be able to find it from our React logic. Without it, we will not be able to render our React app. Had we had this <script> inside the <head> our test page would still work for now, but it would not be suitable for when we will need for it to work with React. So remember, always load your React JavaScript at the bottom of <body>!

11. Install the NPM packages for Babel:

    At this point our infrastructure is capable of processing only the regular browser-safe ES5 JavaScript, not the ES6+/JSX we need to start developing with React. Webpack is just a packer, and it does not know how to translate from ES6+/JSX to ES5 just by itself. To do that, it needs the Babel transpiler. It’s finally time to install Babel!

    Once again we’ll be using NPM to install 2 packages — babel-core and babel-loader. (Same as for Webpack 3). The command for that is: npm install babel-core babel-loader (or 2 separate commands npm install babel-core and npm install babel-loader). At this time the size of my node_modules subdirectory is 140 MB, and previously it was 114 MB. I documented this step in the commit c7f575c84132f04f941b2e1ded2aacad20802ffe.

12. Configure Webpack 4 to use Babel for JSX files

    We have Babel installed, but Webpack does not know about it yet. To tell Webpack to use Babel to transpile ES6+/JSX, we need to tell it to do so in that Webpack configuration file we worked with earlier in step 7 — webpack.config.js. I did this in the example repo commit 85bd9bad3bd5f26ea4bb0cf8531c3ff3df080bbe. Notice that this change to the Webpack 4 config is very different from the corresponding change to the Webpack 3 config — 82cfbe5e03ad314d28fb2a1351ea92a4e4de441d. This configuration schema has changed significantly from Webpack 3 to Webpack 4.

    What has remained the same from the previous tutorials, is that we’re still saying that we want Webpack to “load” files with the file extension .jsx through Babel. Regular .js files will not be going through Babel. This is the Airbnb nomenclature approach, and contrary to Facebook which likes to reuse the .js extension for files containing JSX logic.

13. Prepare JSX entry logic

    Alright, so we just told Webpack to load .jsx files through Babel, but we don’t have any .jsx files yet! So let’s create webpack_in/entry.jsx for our future ES6/JSX logic! I just did this in the example repo commit b14245a0c1eceb3c15ab7cd04ac49ba0dbf48c99.

    Whereas I had entry.js emit the text “JavaScript entry logic” to the console log, I made entry.jsx emit “JSX entry logic”. When we finally test this in a web browser that’s how we’ll know that our configuration is working.

14. Configure Webpack to pack the JSX entry logic

    Now we have told Webpack to use Babel for .jsx files, we have created our webpack_in/entry.jsx, but we still need to tell Webpack to actually pack that new file. Just like with webpack_in/entry.js, we must add webpack_in/entry.jsx to the entry array in webpack.config.js. I did this in the example repo commit c4ebaf6f4be89ae73f7ba079303059e207f06331.

15. Verify proper packing and interpretation of both JavaScript and JSX entry logics

    It’s time to run ./node_modules/webpack/bin/webpack.js --config ./webpack.config.js to pack our JS and JSX files together, deploy the test page, and test it with a web browser! This will verify that everything we did up to now is working. I just deployed it here.

    If you look in the browser console log, you’ll see that there are now 2 entries, the 1st for JavaScript, and the 2nd for JSX. This verifies that the logic in both of our entry files is reaching the browser, which is exactly what we want.

16. Install Babel transpilation presets for ES6+ and JSX

    We’re almost ready to work with React, but still not quite there yet. Just as with Webpack 1 and 3, to tell Babel that we actually want to translate / transpile ES6+ and JSX, we must specify certain “presets“. These presets are referred to by the tokens env and react. The former is for ES6+, and the later is for JSX. (These are the same presets as for Webpack 3 in the previous tutorial.) Before we can even specify these presets in the configuration, we have to install their NPM modules, with the commands: npm install babel-preset-env and npm install babel-preset-react (These tokens can be combined into a single NPM command, but I’m listing 2 commands for better clarity.) I documented this in the example repo commit 97eaeea0bf803465e8d556a6d9ca1f7e47cfbaf9.

    My local node_modules folder grew from 140 MB to 153 MB and 154 MB after completing this step.

17. Configure Webpack 4 to tell Babel to transpile ES6+ and JSX

    And now we need to add the Babel / Webpack configuration to use the presets. I just did this in the example repo commit 93e21306de0932b0fecd4fd6b2a98c147024cd09. As you can see this is another relatively minor addition of just 3 lines. In fact our whole Webpack configuration file is only 27 lines long, and that’s including the comment header and the blank separator lines. Our configuration is at the minimum it can be, plus now we’ve got our project infrastructure up to the point where we’re ready to work with React!

    Note that this change for Webpack 4 configuration is different to the corresponding change to the Webpack 3 configuration in the previous tutorial, which is ab77c4dba397e64b696d9d6307f8ec011f7a871e. For Webpack 4 we’re using the configuration sub-field options rather than query.

Working with React and React DOM

1. Install NPM packages for React

   Hooray! We’re now ready to work with React. This procedure has not changed at all in our migration from Webpack 1 to Webpack 3 to now Webpack 4, but the git commits across the Webpack-specific branches in the example repo are different.

   The first thing we need to do to work with React is install the NPM packages react and react-dom with the commands: npm install react and npm install react-dom I have documented this in the example repo commit 7f2a1a91152e59e6e379aa9d8729d658badc3aa1.

   After installing these packages, my node_modules/ folder grew from 154 MB to 172 MB.

2. Prepare root container element to render React app into

   Next, we need to prepare our future React app root container element inside our test page. The container element is nothing but an empty opening and closing tag that we will specify to React DOM to render our app in. The way React DOM works is that it dumps the previously discussed virtual DOM into this container element. Any previous contents of this container element will get deleted when React DOM does this, so that’s why we’re going to just have an opening and a closing tag.

   I’m going to specify a tag id for this container to be able to use the ancient document.getElementById(...) browser API call to obtain a reference to the element to feed to React DOM. This is how it is normally done when deploying a React app inside a web page. Using the raw DOM API has waned in popularity over the past decade in favor of using the much more flexible and comprehensive jQuery API; however, while still possible, using jQuery is frowned upon when developing with React. And this is actually the only direct DOM API call that we will be making.

   Using jQuery inside React apps is frowned upon because while jQuery is all about the DOM, React has the completely opposite philosophy of never touching the real DOM except when obtaining the root container element as we’re doing right now, or rendering to it from its virtual DOM. Had we included jQuery into our project, at least for the purposes of this demo, it would end up as mostly dead code, needlessly eating up space and bandwidth. There’s nothing remarkable our test app will be doing to need jQuery.

   The container element itself can be any tag, and for this tutorial I’m just going to use a plain <div> with an id of react-app. I cherry-picked this into the example repo commit a7928eb1e1a06ebdb596c2341e3795e2470beee7.

   The most crucial detail in this step is that the root container element needs to be above the <script> tag loading the React app JavaScript logic. This is so that this element is rendered before the JavaScript logic does that document.getElementById(...) call to obtain a reference to it. Otherwise there would be no element to obtain a reference to, and therefore nowhere to render our app into. This has been discussed earlier in step 10 of the build infrastructure preparation procedure in which we explicitly placed that <script> tag just before closing the <body> of our test page.

3. Implement initial React app

   And at this point we’re ready to start writing our React app inside webpack_in/entry.jsx! I just did that in the commit 8a1ce52c4aec1e850fee000b52d45fc8adfbf71f.

   Staying true to the name of this tutorial, I made the app absolutely as minimalistic as it can be — all it does is render a <div> containing the text “Hello! I’m a React app!!”, and this is all accomplished using just 3 lines of code.

   1. We import react.
   2. We import react-dom.
   3. We call ReactDOM.render(...) to render the JSX markup for our app into the root container element.
   And there you have it! A bare-minimum React app!

   You may be wondering why I did not make it 2 lines rather than 3 by omitting the import of react, since I don’t actually call its API directly in this initial implementation. It turns out that this import is a necessary dependency for the method ReactDOM.render(...) to work. In any case, by convention we use that method to render the JSX markup for our root widget, but have that root widget be defined separately using the react package API, so if we were to continue developing this app we would be working directly with that package as well.

4. Transpile React app and verify rendering in browser

   Now that we have the webpack_in/entry.jsx ES6/JSX logic for our app ready, we need to transpile it to webpack_out/minimalistic_react.js ES5 logic, deploy it, and test it in a web browser. As before, we build / transpile with the command ./node_modules/webpack/bin/webpack.js --config ./webpack.config.js, and upon deployment our app looks like this.

   Upon looking at the app test page we will see the string “Hello! I’m a React app!!” rendered into the DOM into that root container element <div> we prepared in step 1. If we look into the web inspector console, we will see the line “JavaScript entry logic.” followed by “JSX entry logic.” This confirms that our entry logic has been transpiled properly.

   You may also see a console message “Download the React DevTools for a better development experience” followed by a URL or similar. Facebook has created an additional in-browser debugging tool for React applications, offers it as browser extensions, and also inserted special logic into the React DOM toolkit to promote it via the console log on non-production builds when the browser extension has not been detected. If you install this extension into your browser this informational message will no longer be emitted, and you will instead get a new “React” tab in the browser’s web inspector when you view pages that use React. This React tab will let you inspect React components of a React app in a similar fashion to the DOM Inspector. You can try it out on the current test page (but you’ll see only its one and only component) and on other web sites currently known to use React DOM directly, such as Instagram and Airbnb.

   Another interesting thing worth mentioning is that our webpack_out/minimalistic_react.js is currently 715 KB on my system (down from 790 KB with Webpack 3), and all we’re doing is rendering a single line! Server-side gzip compression, if enabled on the web server, can compress this down to 164 KB of actual download size, but it is still quite a hefty chunk. Obviously this bloat is not from our 3 lines of code, but from all the React logic underneath. The silver lining here is that this download size will not grow by much as we add more of our own logic to the app. Nevertheless, this is still unacceptable for a production build, which is OK, because this was a development build. Doing a development build included a lot of extra debugging logic into our JavaScript, and also left it unminified. We can significantly cut down on this bloat and minify things if we do a production build, which is what we’re going to do next.

Minifying React web apps for production

1. Configure Webpack for production build

   So 715 KB raw / 164 KB gzipped is a little too much for production, and we need to slim it down. Since we’re building our releases with Webpack, we’ll once again be working with the Webpack configuration file webpack.config.js to add settings to do a production build.

   The required modifications to the Webpack config are relatively minor, and even less than with Webpack 3 in the previous tutorial. Unlike Webpack 3, Webpack 4 does not need any special plugins for minification. We only need to tell Webpack 4 that we’re not in the development mode any more. There are 2 ways to do it — (1) just remove the configuration line mode: 'development' since Webpack 4 does production builds by default, or (2) for better clarity, change the configuration to mode: 'production'. No additional NPM installs will be required for what we’re doing. And I just committed the webpack.config.js production configuration change as 81849d9cb834d0321b57ba6671033414ee78fc7f.

2. Verify and evaluate production build

   Now that we have changed our Webpack configuration for production, it is time to run it again to do our production build. Whereas we had to specify an additional command line parameter -p with Webpack 3, we don’t need to do it now with Webpack 4 since we already told it to be in the production< mode in the previous step. So our build command remains ./node_modules/webpack/bin/webpack.js --config ./webpack.config.js. (Had we not changed mode in webpack.config.js, we could still use the -p parameter to explicitly force production builds.)

   However, the Webpack 'watch' command used earlier to have it auto-re-bundle our code whenever we change it in the course of development is no longer applicable in the production branch, so I removed it from the production branch build instructions in the commit 3d0e21f22d8a39d16390b044dd7a64b13403cf1a.

   Our new webpack_out/minimalistic_react.js is now 101 KB raw size. (Same as with Webpack 3.) That's still not too small, but over 7 times smaller than what it used to be. Let's test the new production build here.

   So everything still works, the React DevTools promotion is no longer appearing even if the browser plugin is not installed, and, best of all, our downloaded web server auto-gzipped size is now 32 KB. That's pretty efficient!

Getting even higher performance and efficiency with Preact

It can be argued that React has made the traditional JavaScript toolkits obsolete, and it can now also be argued that React DOM has in turn been obsoleted by some of its drop-in replacements that appeared over the last couple of years. What is a React DOM drop-in replacement? It's a toolkit duplicating the React API and its philosophy of virtual DOM in the sense that it behaves just like React, but with a different implementation. Why would there be a need for such a toolkit? Well, as discussed in the previous section, using React in a web app can result in relatively large ES5 output file size. Preact is a React API clone that can be substituted into a React web app in place of React without having to rewrite any app logic, and provide the benefit of having much smaller ES5 output file size.

Preact is just one of many React API clones / drop-in replacements. There's also another such toolkit called Inferno, but in this tutorial we're going to be working with Preact to see how much smaller we can get our webpack_out/minimalistic_react.js.

1. Install NPM packages for Preact

   The first thing we need to do to get started with Preact is to install its NPM modules preact and preact-compat. The later is what duplicates the React API to use the former. We're going to install these modules with the command: npm install preact preact-compat I've documented this in the example repo commit 8205f48d32d6100b67d5b37dbddb458982832133. Notice that I did not remove the instructions for installing React and React DOM. Just like in the previous tutorials, these are useful to keep in case we run into some weird future problem in the course of our app development, and decide to temporarily go back to the regular React to check if the problem could be caused by the drop-in replacement. (If we wanted to get really fancy, we could set up automated integration tests to verify the performance of our build under multiple environments.)

   The size of the node_modules/ on my development machine was 172 MB before I installed Preact, and it was 175 MB after. (This is the same 3 MB increase as in the Webpack 3 tutorial. Even though we're using a newer version of Webpack, we're still using the same versions of the Preact packages.)

2. Configure Webpack to substitute Preact for React

   Now that we have installed Preact, we need to tell Webpack to actually use it. So we modify our good old webpack.config.js to substitute Preact for React. I just did that in the example repo commit c9c8bdc432849a544c906da568285069d84a4a42. As you can see, I "alias"-ed Preact in, exactly as with Webpack 1 and Webpack 3. Now when Webpack will be trying to get React it will actually be getting Preact. The key take-away here is that I did not have to modify anything in entry.jsx where the actual React web app lives, and if we ever want to go back, we can just comment-out these 6 lines, and we'll be back with the plain React. It's incredibly easy, and the Webpack configuration schema for this option has not changed at all between versions!

3. Verify and evaluate Preact development build

   OK, time to run ./node_modules/webpack/bin/webpack.js --config ./webpack.config.js to test our app with Preact. We're doing a regular development build for now. And the output webpack_out/minimalistic_react.js on my machine is now 98 KB raw size (8 KB more than with Webpack 3), while the raw size with React was 715 KB. We can look at the Preact development build test page here to see that everything still works, except that the React DevTools no longer finds our app. Preact eliminated the DevTools linkage for maximum efficiency, but if we need to debug our app again we can just temporarily comment-out that alias in Webpack config.

   Our gzipped development build turned out to be 24.7 KB, while with React it was 164 KB. Who needs production builds! Well, we still do, it's just that our current minimalistic app only renders a single <div>.

4. Configure Webpack for Preact production build

   Our evaluation of Preact would not be complete without a production build. This is exactly the same as configuring a React production build. Just as before, we need to modify the Webpack config to take it out of the development mode as outlined in step 1 of the React production section. I just cherry-picked that commit as f05eb0c51a03c2b7d9f00e3999d4d1d324709e25.

5. Verify, evaluate, and be amazed at Preact production build

   Same as for a React production build, we have to modify our BUILD_INSTRUCTIONS to remove the Webpack watch command. I just cherry-picked that build instructions commit as a2d8ff215d4d9fe65bce0280e94e9ae651ae836d.

   And the Preact production output of webpack_out/minimalistic_react.js on my system is currently 22 KB (Same as with Webpack 3). If we test this build here we can see that our downloaded gzipped size is 7.8 KB !!! As a disclaimer I should mention that I'm not affiliated with either Preact or React and I was not paid to write this blog.

Simplifying build instructions and securing the build with the NPM package.json config

So far I went through everything step by step for the sake of clarity and demonstration, to give you the best idea of all the distinct elements required to get up and running with React; however, not all of the manual steps mentioned are absolutely necessary. This is especially true for manually installing the numerous NPM packages we installed as part of this tutorial. In fact we can list-out our packages in a configuration file called package.json, and install all of them with a single command of: npm install

Another reason why this is useful is because package names, dependencies, and compatibilities change over time. The NPM packages outlined in this blog will mutate, and sooner or later will accumulate changes that will break the procedure outlined in this tutorial, (just as happened with the previous tutorials for Webpack 1 and 3.) The NPM configuration file package.json allows us to lock-in package versions, giving us an immutable reference to a known working state of our dependencies.

We can use the NPM command node init to generate our package.json. This utility was initially built to publish NPM packages onto the NPM public repository, and for that reason it prompts the user and includes in its output some additional information that I'm going to cut out for now. And so I've added package.json as git commit 59a92e6aef9f34289d865513e9ade3865b66031c into the Preact development branch, and modified the BUILD_INSTRUCTIONS in git commit 39414a1b8f6329cdbaf613a190579a7fdb8d44ac.

Unfortunately, node init does not differentiate between runtime dependencies and development dependencies. Runtime dependencies are those that are included from within the project application logic, and the logic within these dependencies is invoked during runtime (such as to render the app as React does in this case). Development dependencies are those that are not included from within the application logic, but are needed to bundle, deploy, or debug the application, and so on. In this project, the runtime dependencies are:

• preact
• preact-compat
• react
• react-dom

While the development dependencies are:

• babel-core
• babel-loader
• babel-preset-env
• babel-preset-react
• webpack
• webpack-cli

As can be seen in the commit 59a92e6aef9f34289d865513e9ade3865b66031c, I manually separated the development dependencies under the separate field devDependencies. This provides a better separation as to what is needed for what, and makes it easier to reuse this project in other projects, as the development dependencies of a dependency do not need to be pulled in.

How to use the example repo

The example repo is at https://github.com/maratbn/example_step_by_step_minimalistic_react_app and can be cloned and used as a boilerplate for a new React app. The repo contains commits for this tutorial as well as the previous tutorials on using Webpack 1 and 3, but the commits are separated across different branches. The branches that apply to this tutorial all begin with webpack4. These additional Webpack 4 specific branches are:

• webpack4 -- Common configuration logic and commits.
• webpack4--package.json -- Just like webpack4, but with package.json.
• webpack4--production -- Just like webpack4, but with additional changes to webpack.config.js and BUILD_INSTRUCTIONS to produce minimized bundles intended for deployment to production.
• webpack4--production--package.json -- Just like webpack4--production, but with package.json.
• webpack4--preact -- Just like webpack4, but with Preact swapped-in for React.
• webpack4--preact--package.json -- Just like webpack4--package.json, but with Preact.
• webpack4--preact--production -- Just like webpack4--production, but with Preact.
• webpack4--preact--production--package.json -- Just like webpack4--production--package.json, but with Preact.

If you want to use the example repo for your boilerplate, I recommend you base your project off the branch webpack4--package.json or webpack4--preact--package.json. When you want to deploy to production, fork-off a new release branch, and cherry-pick the production-optimizing commits from webpack4--production--package.json or webpack4--preact--production--package.json.

Summary

In this tutorial I went over setting up a minimalistic React app with Webpack 4. The differences in procedure between this and the procedure in the Webpack 3 tutorial are:

1. It was necessary to explicitly specify version 4 for Webpack with @^4.12.1 if not using package.json.
2. The package webpack-cli had to be explicitly installed in addition to webpack.
3. It was necessary to explicitly put Webpack 4 into development mode, as it assumes production mode by default.
4. When in production mode, there is no need to explicitly pass the -p parameter when bundling for production.
5. Webpack 4 comes with the minification logic built-in, so there are no minification plugins to specify in its config.
6. Webpack 4 has a very different configuration schema from Webpack 3 for specifying loaders, including the Babel loader.
7. Webpack 4 has a different configuration schema from Webpack 3 for specifying presets (nested inside the loader schema), using the sub-field options rather than query.

There were no changes to the actual React app implementation, even though in this tutorial we're using newer React packages. Also, the production bundle sizes for the pure React and Preact apps remained the same from the previous tutorial, likely because all the non-Webpack packages used in this tutorial as the same as in the previous tutorial, and the app is too small to take advantage of Webpack 4 optimizations. Nevertheless, Webpack 4 is supposed to be much faster and more efficient than Webpack 3, and this should become noticeable as the app size increases.