Doubt in Document in Template

Question

Hi All,
I am the beginner. I am studying through "InDesignCS3_ScriptingGuide_JS".
In page no 13, there is script 'save a document as a template'
Below script i am not able to understand, Can anyone explain it breifly if you willing.
Lines are below.
var myFileName;
if(app.activeDocument.saved == true){
//Convert the file name to a string.
myFileName = app.activeDocument.fullName + "";
//If the file name contains the extension ".indd", change it to ".indt".
if(myFileName.indexOf(".indd")!=-1){
var myRegularExpression = /.indd/gi
myFileName = myFileName.replace(myRegularExpression, ".indt");
Thanks in advance for all you read my scripts.
Thanks
BEGINNER

Answer 1

well..
the script is very well commented..
if(app.activeDocument.saved == true){
checks if the current active document is saved. This is important because "Unsaved documents have no full name".
myFileName = app.activeDocument.fullName + "";
the fullName property of a document object returns a File object. This line converts that File object to a string (-containing the full path including the file name). The implementation is a bit unorthodox (don't think you will find it in many JavaScript books), but it works. Another way of doing it is: myFileName = app.activeDocument.fullName.toString()
if(myFileName.indexOf(".indd")!=-1){
checks if the string previously obtained contains ".indd". the indexOf() method of the String object returns -1 if the search string is not found. The problem here (and in the next lines) is if the file name is somenthing like: "myStrangeFile.indd.modifiedByStupidUser.indt"
for the rest of the lines I direct you to any general JavaScript beginner tutorials/books. A good reference: http://www.javascriptkit.com/jsref/