JavaScript is Not Java

Every once in a while, I run across someone who thinks that Java and JavaScript are the same thing. Or that they're closely related to each other. This is understandable — they certainly sound related. But they're not. It's more an accident of history than anything else.

JavaScript is a Scripting Language

JavaScript is a prime example of a scripting language. John Ousterhout, of Tcl fame, puts it this way:

According to Ousterhoust, systems programming languages are languages like C++ that are strongly typed and are used to create applications "from scratch". Scripting languages, on the other hand, are languages like Perl or Rexx that are typeless and are used to connect existing components (usually written in another language) together to form a new application or extend an existing application.

If you look closely at JavaScript, it definitely fits the criteria of a scripting language: it has a simple, typeless syntax, and its primary focus is the manipulation of HTML pages (including responding to user-generated events). Although you can use JavaScript to build entirely browser-based applications (this is the approach used by AvantGo in its offline browser-based application development toolkit, M-Business Anywhere — note, AvantGo is now part of iAnywhere Solutions, my employer), most of the time JavaScript is used as the glue that enhances HTML pages by manipulating the properties and events of the components that make up the page.

Java is NOT a Scripting Language

On the other hand, Java is clearly not a scripting language by this definition. When Java first came out, Sun and others promoted its use in building applets — small applications that run within the context of a web page — but that aspect never caught on due to various issues. Java turned out to be a great language for building server-side applications, however — applications where the logic ran entirely on a server and there was either no user interface or a browser-based user interface. Java also found a bit of a niche in the writing of desktop-based applications, though there it primarily appeals to those who need the application to run on multiple platforms.

So why are the two languages confused?

The Infamous Press Release

The problem started when Sun and Netscape issued a joint press release on December 4, 1995 titled Netscape and Sun Announce JavaScript, the Open, Cross-Platform Object Scripting Language for Enterprise Networks and the Internet. (Whew!) You see, up to that point what we now know as JavaScript was known as LiveScript.

According to JavaScript: Past, Present and Future, the Netscape team initially considered using Java as a way to make web pages "more dynamic" but decided that Java was a better option "for buliding components and not simple, easy-to-tweak scripts". So they built their own language and called it LiveScript. It had some similarities to Java, but Java itself has similarities with C and Pascal. The nice thing about LiveScript was that it was truly a scripting language, so you didn't need to compile the code and you didn't need to design classes — you just started coding.

So why was LiveScript renamed to Java? It's one of those classic marketing mistakes that are made when the gap between the marketing people and the people who build and design the technology is too great. True, JavaScript could be used to control applets to some degree — to it, applets were just another component of a web page — but the integration going back the other way around was lacking. The renaming would have made sense if JavaScript was a subset of Java, but the fact is that learning one of the languages doesn't give you any expertise in the other. They are truly independent.

JavaScript is not Java. End of discussion!