JavaScript is THE scripting language of the Web.
JavaScript is used in billions of Web pages to add functionality, validate forms, comunicate with the server, and much more.
JavaScript is easy to learn. You will enjoy it.
So say W3Schools.
Here is what they say JavaScript is:
As you follow along the examples and exercises in this course, please bear in mind that there is no logical order to teaching JavaScript. In order to cover the basics and have them make sense it is occasionally necessary to dive ahead and use some code that has not, at that point, been covered. Bear with it. If you come across something you do not understand ignore it for that moment and concentrate on what you can follow. The course will catch up to you and cover everything that is used in due course.
It is worth having a look at the following resources which will help you with learning JavaScript.
This list is likely to grow as time wears on.