In short, in any kind of programming, you have to learn the basics first. For web frontend, these I think will be: HTML, latest CSS spec, Javascript ES6. After that you can pick up a small library like jQuery. After that, you will know by yourself if you need to learn a particular JS framework.
For backend: A bit of HTML/CSS/JS, a language usable on server side (C#, PHP, Python, maybe Java, maybe JS), SQL and one RDBMS (Postgres, MySQL, SQL Server etc.). After that you can learn about REST, CORS and more advanced stuff. If you reach this point, you will know by yourself what you need to learn next.
In short, in any kind of programming, you have to learn the basics first. For web frontend, these I think will be: HTML, latest CSS spec, Javascript ES6. After that you can pick up a small library like jQuery. After that, you will know by yourself if you need to learn a particular JS framework.
For backend: A bit of HTML/CSS/JS, a language usable on server side (C#, PHP, Python, maybe Java, maybe JS), SQL and one RDBMS (Postgres, MySQL, SQL Server etc.). After that you can learn about REST, CORS and more advanced stuff. If you reach this point, you will know by yourself what you need to learn next.