The JavaScript Guide shows you how to use JavaScript and gives an overview of the language. If you need exhaustive information about a language feature, have a look at the JavaScript reference.
Returns the code of the currently active language.
Returns the direction of the currently active language (ltr or rtl).
readyState should be used sparingly;  L10n.ready() and L10n.once() are usually better suited for controlling when code is run relative to the state of the localization.