Most of the front-end application we are developing right now is either using Angular or React. If you want to further improve your chance to get a web development job or want to do develop modern websites, I also suggest you take a look at popular JavaScript frameworks like Angular and React JS, which are now ruling the world. It will provide more job opportunities and help you to become a full-stack developer, which most of the startup and small companies look after. I highly recommend Java programmers to learn JavaScript, it's only going to help you to get better. Java is also ubiquitous, and many Java web application uses JavaScript and jQuery for client-side scripting and validation. If you are a web developer, it's essential for you to know in and out of JavaScript. Some use JavaScript for client-side scripting and animation, while others use JavaScript on the server-side with libraries like Nodejs and Reactjsit forms the unique triangle with HTML and CSS. There is almost no website that is not using JavaScript in one or another format. JavaScript is probably another language I recommend someone who knows Java, Why? Because it's really ubiquitous.
Earlier I have shared some of the free JavaScript tutorials, and in this article, I am going to share 5 good books to learn JavaScript, which are open to read online or allow you to download PDF for offline reading. Programmers can almost run anything by these free books. The internet is full of good things, and one of them is free eBooks and PDF.