Sådan opbygges din første desktop-app med JavaScript ved hjælp af Electron

Har du nogensinde spekuleret på, om du kan oprette desktop-apps på tværs af platforme med HTML, CSS og JavaScript?

Det er muligt med Electron.

Denne artikel hjælper dig med at forstå nogle kernekoncepter i Electron.

Ved afslutningen af ​​dette indlæg kender du processen med at oprette platform-apps på tværs af platforme med Electron, HTML og CSS.

Før vi kommer i gang, kan du på forhånd tjekke den app, vi skal bygge i denne vejledning.

Hear Me Type har en enkel, men ligetil funktionalitet. Hver tast, der trykkes på tastaturet, spiller en bestemt lyd. Så hvis jeg trykker på “A” -knappen, afspiller appen den specifikke lyd for bogstavet A.

Der er to versioner til download. Kildekoden til denne vejledning og en avanceret version af appen anbefales til mere erfarne elektronbrugere.

Koden ændres, da jeg tilføjer nye funktioner og forbedringer. Sørg for at tjekke tilbage for at se, hvad der er nyt.

Uden yderligere ado, lad os finde ud af mere om Electron og oprette vores første app!

Hvad er elektron?

Electron er en ramme for applikationer på tværs af platforme, der bruger Chromium og Node.js.

Det er nemt at opbygge applikationer på tværs af platforme ved hjælp af HTML, CSS og JavaScript. Din app er kompatibel med Mac-, Windows- og Linux-operativsystemer lige ud af kassen.

Andre indbyggede funktioner er:

  • Automatiske opdateringer - gør det muligt for apps automatisk at opdatere sig selv
  • Indfødte menuer og meddelelser - opretter indbyggede applikationsmenuer og kontekstmenuer
  • Appnedbrudsrapportering - du kan indsende rapporter om nedbrud til en ekstern server
  • Fejlfinding og profilering - Chromiums indholdsmodul finder ydeevne flaskehalse og langsomme operationer. Du kan også bruge dine foretrukne Chrome Developer Tools i din app.
  • Windows-installationsprogram - du kan oprette installationspakker. Hurtig og enkel.

Hvis du er tilfreds med, hvad Electron tilbyder, lad os dykke dybere og oprette en simpel Electron-app.

Før vi bliver snavsede, skal du installere Node.js. Du skal også have en GitHub-konto til at gemme og opdatere din app. Selvom en konto ikke er nødvendig, anbefales den stærkt. GitHub er en industristandard, og det er vigtigt at vide, hvordan man bruger det.

Vi bruger GitHub i denne vejledning.

Kom godt i gang

Når du er konfigureret, skal du åbne et terminalvindue til dit operativsystem.

Følg instruktionerne nedenfor for at klone Electron Quick Start Git-arkivet til din computer.

Vi bygger vores software på 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

Når ovenstående trin er færdige, skal du se, at appen er åben i et browservindue. Og det er faktisk et browservindue!

Vinduesstilen ændres afhængigt af operativsystemet. Jeg valgte at bruge Windows klassiske udseende. Groovy!

Som jeg sagde tidligere, kan du bruge Chrome's Developer Tools i din app. Hvad du kan gøre med din browsers udviklerværktøjer, kan du også gøre inde i appen. Fremragende!

Elektronapplikationsarkitektur

Lad os se på kildekoden og filstrukturen i vores app. Åbn projektet i din yndlings teksteditor eller IDE. Jeg vil bruge Atom, som er bygget på ... du gættede det ... Elektron!

Vi har en grundlæggende filstruktur:

electron-quick-start

- index.html

- main.js

- package.json

- render.js

Filstrukturen svarer til den, vi bruger, når vi opretter websider.

Vi har:

  • index.html som er en HTML5-webside, der tjener et stort formål: vores lærred
  • main.js opretter vinduer og håndterer systemhændelser
  • package.jsoner opstartsskriptet til vores app. Den kører i hovedprocessen, og den indeholder oplysninger om vores app
  • render.js håndterer appens gengivelsesprocesser

Du kan have et par spørgsmål om hovedprocessen og gengive proces ting. Hvad er det, og hvordan kan jeg komme sammen med dem?

Glad for du spurgte. Hæng på din hat, for dette kan være nyt område, hvis du kommer fra browser JavaScript-rige!

Hvad er en proces?

Når du ser ”proces”, så tænk på en proces på operativsystemniveau. Det er en forekomst af et computerprogram, der kører i systemet.

Hvis jeg starter min Electron-app og tjekker Windows Task Manager eller Activity Monitor for macOS, kan jeg se de processer, der er knyttet til min app.

Hver af disse processer kører parallelt. Men hukommelsen og ressourcerne, der er afsat til hver proces, er isoleret fra de andre.

Sig, at jeg vil oprette en, for loopder inkrementerer noget i en gengivelsesproces.

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

Inkrementerne er kun tilgængelige i gengivelsesprocessen. Det påvirker overhovedet ikke hovedprocessen. Den This is a for loopmeddelelse vises kun på den gengives modul.

Hovedproces

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, cre ate a div element with the audio class tag.

Inside the created div element, create an io> element wi th an id of “A” , the source tag of “sounds/A.mp3” and w ith 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:

Now the io> is pointing to an unknown source file. Let’s create a folder c alled 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.