Comment créer votre première application de bureau avec JavaScript à l'aide d'Electron

Vous êtes-vous déjà demandé si vous pouviez créer des applications de bureau multiplateformes avec HTML, CSS et JavaScript?

C'est possible avec Electron.

Cet article vous aidera à comprendre certains concepts de base d'Electron.

À la fin de cet article, vous connaîtrez le processus de création d'applications de bureau multiplateformes avec Electron, HTML et CSS.

Avant de commencer, vous pouvez vérifier à l'avance l'application que nous allons créer dans ce didacticiel.

Hear Me Type aura une fonctionnalité simple mais directe. Chaque touche enfoncée sur le clavier jouera un son spécifique. Donc, si j'appuie sur le bouton «A», l'application jouera le son spécifique pour la lettre A.

Il existe deux versions disponibles au téléchargement. Le code source de ce didacticiel et une version avancée de l'application, recommandés pour les utilisateurs Electron plus expérimentés.

Le code changera depuis que j'ajoute de nouvelles fonctionnalités et améliorations. N'oubliez pas de revenir pour voir les nouveautés.

Sans plus tarder, découvrons plus sur Electron et créons notre première application!

Qu'est-ce que Electron?

Electron est un framework pour les applications de bureau multiplateformes utilisant Chromium et Node.js.

Il est facile de créer des applications multiplateformes à l'aide de HTML, CSS et JavaScript. Votre application sera compatible avec les systèmes d'exploitation Mac, Windows et Linux dès la sortie de la boîte.

Les autres fonctionnalités intégrées sont:

  • Mises à jour automatiques - permettent aux applications de se mettre à jour automatiquement
  • Menus et notifications natifs - crée des menus d'application et des menus contextuels natifs
  • Rapports de plantage de l'application - vous pouvez soumettre des rapports de plantage à un serveur distant
  • Débogage et profilage - Le module de contenu de Chromium détecte les goulots d'étranglement des performances et la lenteur des opérations. Vous pouvez également utiliser vos outils de développement Chrome préférés dans votre application.
  • Programme d'installation Windows - vous pouvez créer des packages d'installation. Rapide et simple.

Si vous êtes satisfait de ce que propose Electron, allons plus loin et créons une application Electron simple.

Avant de nous salir les mains, vous devrez installer Node.js. Vous devez également avoir un compte GitHub pour stocker et mettre à jour votre application. Bien qu'un compte ne soit pas nécessaire, il est fortement recommandé. GitHub est une norme de l'industrie et il est important de savoir comment l'utiliser.

Nous utiliserons GitHub dans ce tutoriel.

Commencer

Lorsque vous êtes configuré, ouvrez une fenêtre Terminal pour votre système d'exploitation.

Suivez les instructions ci-dessous pour cloner le référentiel Electron Quick Start Git sur votre ordinateur.

Nous allons construire notre logiciel sur Electron Quick Start.

# Clone the Quick Start repositorygit clone //github.com/electron/electron-quick-start# Go into the repositorycd electron-quick-start# Install the dependencies and runnpm install && npm start

Lorsque les étapes énumérées ci-dessus sont terminées, vous devriez voir l'application ouverte dans ce qui ressemble à une fenêtre de navigateur. Et c'est bien une fenêtre de navigateur!

Le style de la fenêtre change en fonction du système d'exploitation. J'ai choisi d'utiliser le look classique de Windows. Sensationnel!

Comme je le disais plus tôt, vous pouvez utiliser les outils de développement de Chrome dans votre application. Ce que vous pouvez faire avec les outils de développement de votre navigateur, vous pouvez également le faire dans l'application. Exceptionnel!

Architecture d'application électronique

Jetons un coup d'œil au code source et à la structure des fichiers de notre application. Ouvrez le projet dans votre éditeur de texte ou IDE préféré. Je vais utiliser Atom qui est construit sur… vous l'avez deviné… Electron!

Nous avons une structure de fichiers de base:

electron-quick-start

- index.html

- main.js

- package.json

- render.js

La structure des fichiers est similaire à celle que nous utilisons lors de la création de pages Web.

On a:

  • index.html qui est une page Web HTML5 ayant un seul objectif: notre canevas
  • main.js crée des fenêtres et gère les événements système
  • package.jsonest le script de démarrage de notre application. Il fonctionnera dans le processus principal et contient des informations sur notre application
  • render.js gère les processus de rendu de l'application

Vous pouvez avoir quelques questions sur le processus principal et les choses du processus de rendu. Que diable sont-ils et comment puis-je m'entendre avec eux?

Heureux que vous ayez demandé. Accrochez-vous à votre chapeau car cela peut être un nouveau territoire si vous venez du royaume JavaScript du navigateur!

Qu'est-ce qu'un processus?

When you see “process”, think of an operating system level process. It’s an instance of a computer program that is running in the system.

If I start my Electron app and check the Windows Task Manager or Activity Monitor for macOS, I can see the processes associated with my app.

Each of these processes run in parallel. But the memory and resources allocated for each process are isolated from the others.

Say I want to create a for loop that increments something in a render process.

var a = 1;
for ( a = 1; a < 10; a ++) { console.log('This is a for loop');}

The increments are only available in the render process. It doesn’t affect the main process at all. The This is a for loop message will appear only on the rendered module.

Main Process

The main process controls the life of the application. It has the full Node.js API built in and it opens dialogs, and creates render processes. It also handles other operating system interactions and starts and quits the app.

By convention, this process is in a file named main.js. But it can have whatever name you’d like.

You can also change the main process file by modifying it in package.json file.

For testing purpose, open package.json and change:

“main”: “main.js”,

to

“main”: “mainTest.js”,

Start your app and see if it still works.

Bear in mind that there can be only one main process.

Render Process

The render process is a browser window in your app. Unlike the main process, there can be many render processes and each is independent.

Because every render process is separate, a crash in one won’t affect another. This is thanks to Chromium’s multi-process architecture.

These browser windows can also be hidden and customized because they’re like HTML files.

But in Electron we also have the full Node.js API. This means we can open dialogs and other operating system interactions.

Think of it like this:

One question remains. Can they be linked somehow?

These processes run concurrently and independently. But they still need to communicate somehow. Especially since they’re responsible for different tasks.

For this, there’s an interprocess communication system or IPC. You can use IPC to pass messages between main and render processes. For a more in-depth explanation of this system read Christian Engvall’s article.

These are the basics of processes for developing an Electron application.

Now let’s get back to our code!

Make It Personal

Let’s give our app’s folder a proper name.

Change the folder name from electron-quick-start to hear-me-type-tutorial.

Reopen the folder with your favorite text editor or IDE. Let’s further customize our app’s identity by opening up the package.json file.

package.json contains vital information about our app. This is where you define the name, version, main file, author, license and so much more.

Let’s get a little bit of pride and put you as author of the app.

Find the “author” parameter and change the value to your name. It should look like this:

“author”: “Carol Pelu”,

We also need to change the rest of the parameters. Find the name and description below and change them in your package.json file:

Awesome! Now our app has a new name and a short but straight to the point description.

Remember, you can always run npm start in your terminal to execute the app and see the changes you’ve made.

Let’s move forward and add the expected functionality of our app. We want to play a specific sound for every keyboard key that we press.

Oh, the Fun-ctionalitee!

What is an app without fun-ctionality? Nothing much…

Now we must take care of it and give our app the functionality it desires.

To make the app react to our input, we must first define an element to hook upon and then trigger the desired action.

To do that we will create audio elements with specific ids for the keyboard keys that we want. Then we will create a switch statement to find out which keyboard key was pressed. Then we’ll play a specific sound assigned to that key.

If this seems a little complex to you now, have no fear. I will guide you through every step.

Download this archive containing all the sound files we’ll be using. We’ll soon make use of them!

Open up the index.html file and let’s create the io> elements to embed the sound content in our app.

Inside the dy> element, create a div element with the audio class tag.

Inside the created div element, create an io> element with an id of “A”, the source tag of “sounds/A.mp3” and with a preload attribute of “auto”.

We’ll use preload=”auto” to tell the app that it should load the entire audio file when the page loads. index.html is the main file of the app, and all our sound files will load when the app executes.

The code should look like this:

Original text


Now the io> is pointing to an unknown source file. Let’s create a folder called sounds and unzip all the sound files inside the folder.

Great! The only important thing that’s missing right now is the JavaScript code.

Create a new file called functions.js. Let’s require it within the index.html file so that the JS code is ready for use when the app is running.

Following the example of require(./renderer.js'), add this line of code right under it:

require('./functions.js')

Your project should look like this:

Outstanding! Now that we have everything stitched up, it’s time for the moment of truth.

Open up the functions.js file and add the following JavaScript code into the file. I’ll explain how it works in just a moment.

document.onkeydown = function(e) { switch (e.keyCode) { case 65: document.getElementById('A').play(); break; default: console.log("Key is not found!"); }};

The code should look like this:

Open your bash or Terminal window. Be sure you’re in your project’s folder and type npm start to run the app.

Tune up the volume of your speakers and press the A button on your keyboard.

#MindBlown

The JS code is pretty simple and straightforward.

We use the onkeydown event on the document object to find out which HTML element is being accessed. Remember, the document object is our app’s main window.

Within the anonymous function, we use a switch statement. Its purpose is to identify the Unicode value of the pressed keyboard key.

If the Unicode value of the pressed keyboard key is correct, the sound is played. Otherwise a “not found” is error is thrown. Look for the message in the console.

What a ride!

You may have noticed that we have sound files to cover A-Z and 0–9 keys. Let’s use them too so they don’t feel the bitter taste of loneliness.

Head over to index.html and create an io> element for every key that we have a sound file for.

The code should look like this:

Yeah, of course you can copy-paste:

Awesome! Now let’s do the same thing for the JS code within functions.js.

You can find the char codes (key codes) on this website.

But yeah, you can copy-paste this too:

document.onkeydown = function(e) { switch (e.keyCode) { case 48: document.getElementById('0').play(); break; case 49: document.getElementById('1').play(); break; case 50: document.getElementById('2').play(); break; case 51: document.getElementById('3').play(); break; case 52: document.getElementById('4').play(); break; case 53: document.getElementById('5').play(); break; case 54: document.getElementById('6').play(); break; case 55: document.getElementById('7').play(); break; case 56: document.getElementById('8').play(); break; case 57: document.getElementById('9').play(); break; case 65: document.getElementById('A').play(); break; case 66: document.getElementById('B').play(); break; case 67: document.getElementById('C').play(); break; case 68: document.getElementById('D').play(); break; case 69: document.getElementById('E').play(); break; case 70: document.getElementById('F').play(); break; case 71: document.getElementById('G').play(); break; case 72: document.getElementById('H').play(); break; case 73: document.getElementById('I').play(); break; case 74: document.getElementById('J').play(); break; case 75: document.getElementById('K').play(); break; case 76: document.getElementById('L').play(); break; case 77: document.getElementById('M').play(); break; case 78: document.getElementById('N').play(); break; case 79: document.getElementById('O').play(); break; case 80: document.getElementById('P').play(); break; case 81: document.getElementById('Q').play(); break; case 82: document.getElementById('R').play(); break; case 83: document.getElementById('S').play(); break; case 84: document.getElementById('T').play(); break; case 85: document.getElementById('U').play(); break; case 86: document.getElementById('V').play(); break; case 87: document.getElementById('W').play(); break; case 88: document.getElementById('X').play(); break; case 89: document.getElementById('Y').play(); break; case 90: document.getElementById('Z').play(); break; default: console.log("Key is not found!"); }};

Our app is now complete! Congrats!

The main functionality of the app is finished, but there is still work to be done!

Polska ja! (Polish me!)

Even though the app is functional it still lacks some things here and there.

For example, within theindex.html file, you can change the app’s title and the content for the main window.

Moreover, the app has no design, no beautiful colors, and no pictures of either cats or dogs.

Free your imagination and find ways to improve the app’s design.

The code isn’t perfect either. We have lots of identical code which can be optimized and improved. This will result in fewer lines of code and it’ll be less painful for the eyes.

Duplicate code is bad practice!

Test It! Just Test It!

Good software must be thoroughly tested.

I suggest you begin by pressing every keyboard key to see what’s happening.

The best scenario is you will hear the audio for every keyboard key you have specified in the code. But what will happen when you press many keys in a row as fast as you can? What about keys that are not even supposed to be pressed like the Home and NumLock buttons?

What if you minimize the app and try to press a key? Do you hear a sound? And what happens when you don’t have the app window selected and you press a keyboard key, do you still hear any sounds?

The answer is unfortunately no.

This behavior is because of the architecture upon which Electron was built. It allows you to get global keys like you can do with the C# language, but you can’t register individual keystrokes. This is outside of the realm of normal use-cases for an electron application.

Run through the code line by line and try to break it. See what is happening and what kind of errors Electron is throwing. This exercise will help you become better at debugging. If you know the flaws of your app you then know how to fix them and make the app better.

In the functions.js file, I have intentionally used a deprecated JavaScript event. Can you spot it?

Once you find it I would like you to think about how you can replace it without changing the app functionality.

Using deprecated code is bad practice and can lead to serious bugs you might not even know exist. Stay current with the documentation of the language to see what might have changed. Always stay up to date.

Conclusion

I would like to thank and congratulate you for reaching this point!

You now have the knowledge to create a simple cross-platform Electron app.

If you want to dive deeper into Electron and see what I am working on check out Hear Me Type and my profile on GitHub.

Feel free to clone, fork, star and contribute to any of my public projects.

Please come back and read again this article from time to time. I will modify it to keep current with Electron updates.

Thank you so much for taking the time out of your day to read my article.

This article was originally posted on NeutronDev.com.

If you’d enjoy more detailed articles/tutorials about Electron, click the ? below. Feel free to leave a comment.