The basic method

One javascript file per language.

Say Hello Say Hola

Very, very simple this one. Both HelloWorld and Hola call a javascript function called greet(); They both include a link to the javascript file that is relevant to them.
greet() is defined in both Greetings-en-GB.js and Greetings-es-ES.js In Greetings-en-GB.js it is defined as
function greet()
{
  document.writeln('Hello!');
}

Get files:

• HelloWorld.html
• Hola.html
• Greetings-en-GB.js
• Greetings-es-ES.js