Jay Braun
9/2/2015 9:43:00 PM
> Is it a language, or a set of library routines? If
> the latter, how are they accessed?
It is a language designed to run in a web browser. It adds dynamic behaviors that static HTML pages cannot perform.
> Is it used, or useful, for anything besides hovering
> the cursor over an image on a Web page?
A little Googling will convince you that is is.
> What is its relation to Java, as a plug-in? Are they
> independent? Does Javascript execute/reside 'inside'
> Java, so to speak?
JavaScript was originally called Mocha, then LiveScript by its inventors at NetScape. The name JavaScript was intended to take advantage of Java's growing popularity in the mid-to-late 1990s.
While the two share some syntactic heritage from C, they are independent languages designed for distinct purposes. Java programs execute in the JRE/JVM, while JavaScript generally runs in a browser. There are some "server-side" platforms for running JavaScript, such as Node.js, as well as a version of JavaScript that runs in the JRE, called Rhino. But JavaScript is *not* a subset of variant of Java.
There is also something called BeanShell, which is essentially scripted Java that can run inside the JRE, even as part od a Java application, but it has nothing to do with JavaScript. (I mention it because the name JavaScript would have been an ideal name for BeanShell, but it was already taken.)
> What are the limitations of the language, in terms of
> hardware, memory access, security, etc.?
Think of it as a programming language whose platform is the browser. So, while it is expressive and powerful, you cannot access your operating system's file system, TCP ports, and other resources outside the browser.