JavaScript is a core programming language on the Web technology set. As its name let clear, at some point it was inspired on the (1995) Java language. But in fact, despite a few similarities on the most basic lexical structure they both have inherited from the (1972) C language, it turned out they are completely different beasts. For instance, in terms of OOP implementation, while Java is class-based as (1985) C++ is, JavaScript embraces the prototype-based approach inspired on other less-known projects.
In the historical moment JavaScript came to light it was probably the most familiar, the more lightweight and flexible scripting language bringing some basic dynamics to HTML content. Soon it became clear its great potential in creating Web applications beyond mere static content. That should be the most convincing explanation why it turned out to be one of the core technologies driving the Web.
The support and standardization of JavaScript didn't appear right from the start as most state-of-the-art languages of nowadays. Only about 2 years later after JavaScript's first appearance the first standardization effort was delivered. And since that time a myriad of JavaScript engine projects have emerged with varying degrees of support and standardization battling for acceptance. Naturally, that scenario complicated quite a log developers' matters, needless to say the business challenges on time and cost of targeting a project to multiple implementations in a consistent way. Fortunately, by 2018 the industry has agreed in addressing this issue and things are now better although there's still a lot to do on near future.
As to OOP JavaScript's prototype-base approach is very attractive because of its flexibility and fast engineering life-cycle. For Web applications which is typically asynchronous, if carefully planned, it may be a clear better choice, even considering the greater run-time performance of other compiled-languages. In addition, its thin-client characteristic on front-ends simplifies a lot of administration and enhances security.
In summary, JavaScript is worth-while learning.
