Java is an Object Oriented Programming (OOP) language created by James Gosling of Sun Microsystems. JavaScript was created by the fine people at Netscape. JavaScript is a distant cousin of Java. It is also an OOP language. Many of their programming structures are similar. However, JavaScript contains a much smaller and simpler set of commands than does Java. It is easier for the average weekend warrior to understand.
The main difference is that Java can stand on its own while JavaScript must be placed inside an HTML document to function. Java is a much larger and more complicated language that creates “standalone” applications. A Java “applet” (so-called because it is a little application) is a fully contained program. JavaScript is text that is fed into a browser that can read it and then is enacted by the browser.
Another major difference is how the language is presented to the end user (that’s you when you’re surfing). Java must be compiled into what is known as a “machine language” before it can be run on the Web. JavaScript is text-based. You write it to an HTML document and it is run through a browser. You can alter it after it runs and run it again and again. Once the Java is compiled, it is set. Sure, you can go back to the original text and alter it, but then you need to compile again.
Java applets run independent of the HTML document that is calling for them. Sure, they appear on the page, but the HTML document did little more than call for the application and place it. If the programmer allows it, oftentimes parameters can be set by the HTML document. This includes the background color of the applet of the type of text it displays, etc. The delivery of the applet is done through a download. The HTML document calls for the application, it downloads to the user’s cache, and waits to run. JavaScript is wholly reliant on the browser to understand it and make it come to life.
JavaScript’s main benefit is that it can be understood by the common human. It is much easier and more robust than Java. It allows for fast creation of Web page events. Many JavaScript commands are what are known as Event Handlers: They can be embedded right into existing HTML commands. JavaScript is a little more forgiving than Java. It allows more freedom in the creation of objects. Java is very rigid and requires all items to be denoted and spelled out. JavaScript allows you to call on an item that already exists, like the status bar or the browser itself, and play with just that part. JavaScript is geared to Web pages. Java is geared toward where it is needed most at the time.