My course conclusion work is about a linear algebra mobile app. It is a simple app, basically the user logs in and when logged in there will be som...
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Depends on your background! If you're already somewhat familiar with web development and JavaScript (especially React), then using React Native is a great way to get started with mobile development.
Your other option in this space is Flutter - you'll have to learn a new language for it as it's all written in Dart. But it's by Google and they are very invested in making this popular, so there should be plenty of resources.
Otherwise if you'd like to focus on a single platform (iOS or Android), you can always build a native app in Kotlin / Swift. I don't know the best getting started guide for Android, but for iOS, there is a free comprehensive course published by Stanford university that is updated each year and is an amazing getting started point for native iOS development.
And finally, there's always the option of building a really good website that is flexible enough to work well on smaller (phone) screens to cover all platforms in one. There are all kinds of ways to make your website look and feel like a native app!
If you know Javascript, try NativeScript or Ionic. You can write javascript while using apis to access native mobile functionality without the need to learn Android or iOS programming.
better to use flutter compared to react native.
But I don't have any contact with Dart. JavaScript I know the basics.
Why not web based and use react instead then? You can argue it's an app, but a web app.
Btw, you can spend 1 month to get used to dart. If you already can code, dart is not that hard. Also, if you are planning to enter the mobile app dev work, flutter is on the rise right now. So it will be worth learning in a long run.