Scripting Language and Compiled Language

Question

I have two questions:

1. How does Jquery/ MooTools extend the syntax of Javascript? I mean why can you just have new syntax for Jquery and MooTools that does not exist in Javascript?
2. Since MooTools allows user to have class, inheritances. Interpreted language like this is getting closer to compiled language. Will they eventually replace Java (which runs on JVM)? Or are there specific aspects of Java that extension to Javascript will never achieve?

It may be foolish questions but I really want some keywords to explain them.

Thanks

Answer 1

One way that JQuery gives the impression of redefining the language is with the $ operator. What may not be clear however is that $ is just a function declared at window (global) scope, since $ is a valid variable name in JavaScript:

From the source:

jQuery = window.jQuery = window.$ = function( selector, context ) {
    // The jQuery object is actually just the init constructor 'enhanced'
    return new jQuery.fn.init( selector, context );
},

Answer 2

They are not extending the syntax of javascript per say. They still have to abide by all the grammar rules of javascript.