There are many reasons to learn a new programming language; natural curiosity, upskilling, a new career or you just want to compliment an existing skillset.
This isn't a top programming languages list, it is a list of languages that will give you the chance to net a higher salary, learn a sought-after language or progress in your career. These listed languages are practical and packed with opportunity.
Javascript
Javascript is the worlds most popular language, at least according to StackOverflow's annual developer survey. Since ES2015, Javascript has been on a yearly release schedule and continues to get better.
There is no other language like Javascript, as more and more devices become web-enabled, any device that connects to the internet can most likely run Javascript. The core concepts you learn writing Javascript can also be applied to numerous other programming languages.
Javascript is a language that will always allow you to find a job, it will forever be one of those much sought after languages and that is the reason it is number one on this list.
Rust
Once again, citing the popular StackOverflow developer survey, for the second year in a row Rust is the most loved programming language. It is a Mozilla Research sponsored language and arguably has some really nice features.
Rust is typesafe, concurrent and while syntactically similar to C++ it offers much superior memory safety which is important for high performing applications. This is a language that is relatively new, so it's an emerging language and great opportunity for you to get in on the ground floor and get a high paying Rust position.
Even better, the latest and greatest version of Mozilla's Firefox browser has a new rendering engine called Serv written in Rust and the source code is available on Github, which I highly recommend checking out because it gives you some quality insight into a largescale Rust application.
Best of all, if you know Javascript than a lot of aspects you have learned will also apply to Rust. There are more than a few similarities between the two, making it a great gateway language.
Python
Python is a general-purpose language which you can find almost anywhere today. You might not hear about it as much as you do Javascript or other languages, but Python is everywhere. One of the biggest Python users is Google, not known by a lot of people but many of the core parts of Google's search platform are written in Python.
The language utilises the concept of indentation and space, so unlike Rust or Javascript, you don't use curly braces or semicolons, just space. It's an elegant language, used by Google and even NASA. It has frameworks for web applications, packages for desktop apps, great for writing scrapers or parsing things.
Kotlin
Kotlin is a statically typed programming language that runs on the Java virtual machine and also can be compiled to JavaScript source code or use the LLVM compiler infrastructure. The project is run by the JetBrains team (a company known for WebStorm and Resharper).
Kotlin is fast becoming a well-liked and sought after programming language, Kotlin is designed to interoperate with Java code, but it is not compatible with Java code (even though it has dependencies on Java libs). One emerging use-case for Kotlin is for building modern Android applications.
Other notable mentions and worthy languages; Swift, C++, Go, Ruby.
Programming is developing so fast, so many new languages. I only heard of 2 of the languages on this list. I want to learn Python sometime.