Many people assume just because JavaScript has “Java” in its name that the two are somehow related. Although most programmers will roll their eyes at this confusion, the history of the two programming languages did intersect for a short moment during the early days of Netscape. But the evolution of the two took wildly different paths from that point on. There’s a joke that Java is to JavaScript as ham is to a hamster, if that clears up any misunderstanding.
If we traveled back in time about five years ago, there would be a simple comparison: Java is a general purpose programming language, and JavaScript is used on websites to make them animated and interactive. Since JavaScript has evolved, the comparison is now a bit complicated. Below are similarities and differences from a web development perspective.
Both can run in a browser
As you’re likely aware, JavaScript runs on most modern browsers, and many websites take advantage of this to enhance the user’s experience. Java applets can also run in a browser, but have been declining in popularity for multiple reasons, including compatibility and security.
Both can run on a server
Java is known as a workhorse with application servers such as WebSphere and JBoss running a large portion of the web applications seen by both users on public sites and those behind workplace firewalls. JavaScript has dabbled in the server-side world for a while, but the recent popularity of Node.js is causing more JavaScript-powered application servers to spring up all over.
Both have libraries and frameworks
Libraries and frameworks help programmers by providing access to general and purpose-specific code that can be reused over and over again for different products. Both Java and JavaScript have a wide range of library and framework options available to assist developers in a variety of scenarios.
Compiled vs interpreted
Java code is written in an Integrated Development Environment (IDE) and compiled into bytecode, which is not readable by humans, though any Java Virtual Machine (JVM) should be able to run it. On the other hand, JavaScript code is typically executed by a JavaScript engine in the same syntax in which it is written. Making changes in Java application environments can require multiple steps using specialized software, while making changes to JavaScript can sometimes be done with a simple text editor.
Two-stage vs. runtime-only debugging
Because Java is compiled before it can be run, any structural problems with code quickly becomes apparent. Once running, IDEs often enable the developer to attach to the JVM to debug in real-time. JavaScript is not compiled in the same way, so all bugs are found during runtime. The debugging capabilities of JavaScript are dependent on the execution environment, which can vary widely.
Source: Segue Tech
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