Tarn Barford

JavaScript is a slightly flawed language but it's got elegant parts too. All languages do to some degree, it's just JavaScript seems to have both in extremes. Whatever you think of it, history has made it the language for scripting the client-side web. It has become a mainstream language that shows no sign of falling off.

The excelent book JavaScript: The Good Parts by Douglas Crockford, working with the jQuery library and learning a little Lisp has lead me to really embrace JavaScript.

It's no secret that I like programming with interactive consoles and decided I wanted find out if there was an interactive console for JavaScript. A language that only lives inside web browser environment didn't seem right to me.

Rhino is a JavaScript implementation on the JVM. It has a compiler, a debugger and interactive console.

To get started you obviously need a version of the JVM. That's not to difficult. On Windows I just downloaded a Sun Java 6 installer. On my Ubuntu install I installed openjdk but found Rhino didn't work. So I installed sun-java6, which worked.

sudo apt-get install sun-java6-bin sun-java6-jre sun-java6-jdk

You can find what version you've installed by running

$ java -version
java version "1.6.0_15"
Java(TM) SE Runtime Environment (build 1.6.0_15-b03)
Java HotSpot(TM) Client VM (build 14.1-b02, mixed mode, sharing)

Excellent. The Rhino binaries includes js.jar which is needed for the console. Now should be able to run the jar

$ java -jar js.jar

When all goes well this will take you into the Rhino shell

Rhino 1.7 release 2 2009 03 22
js>

We can start playing with the language.

js> get_counter = function() { var counter = 0; return function() { 
     print(counter); counter++; } };
..
js> counter1 = get_counter();
js> counter1();
0
js> counter1();
1
js> counter2 = get_counter();
js> counter2()
0
js> counter1()
2

Which is cool and there is some of the weirdness

js> '5' + 3
53
js> '5' - 2
3

And some interesting features

js> parseInt('06')
6
js> parseInt('08')
NaN
js> parseInt('10')
10
js> parseInt('010')
8

I'm looking forward to learning more about writing code in JavaScript.

OMG. It's a JavaScript Rhino