Naming PDF at export using a portion of IDCS4 File name(JS)

Question

I have a script that will use a PDF Export Preset to export each page of a document individually. The script uses the ID document's name and adds an "_Final".
For example:
ID docs name:
138-140 TEST 10_WORKER.indd
Final PDF's name:
138-139 TEST 10_WORKER_Final_1.pdf
138-140 TEST 10_WORKER_Final_2.pdf
138-140 TEST 10_WORKER_Final_3.pdf
The first three numbers represent the first page number in the document. I would like it to use these numbers and progressively add one to the following PDF page numbers. I am looking for it to do this while using our standard naming convention which looks like this. . .
MYTEST_138.pdf
MYTEST_139.pdf
MYTEST_140.pdf
Any guidance would be greatly appreciated. Thanks!

Answer 1

The substr(start,length) stuff is in the OMV (under Javascript's Core Classes, class String -- and if you are interested in further developing your JS skills you might want to check my version of this clumsy system!).
Shonky cuts off the first three characters and instructs Javascript to forcibly convert them to a number -- the parseInt command (and that's in the OMV Core Classes under "Global"). parseInt returns the numerical value of the string if it contains digits, or the special value NaN ("Not-a-Number") if it's not. Hence the 'typeof' check -- which, incidentally, I didn't know, but I can guess at what it does. I bet it returns 'true' if the variable contains a number, 'false' if not; and NaN is per definition not a number. (That's computer logic, that is!)
The check is necessary because you want to add something to it as a number; and JS also allows 'adding to a string'. Suppose the first three characters are "hey", adding 1 to it would return the syntactically correct result "hey+1", but it's not what you want here (more computer logic!).
The GREP you point to is quite a bit smarter than assuming the first three, and only three, characters are in fact digits. Some testing shows that this
n = decodeURI(app.activeDocument.name).replace(/^(\d+).*/, '$1');
alert (n);
returns one single string consisting of all digits at the front of your file name. I had to try this out one character at a time ... but, eventually, it boiled down to this:
^(\d+).*
^  start of text
(..) group number 1
\d any digit
+ one or more of the preceding code
. any character
* zero or more of the preceding code
$1 recall found group number one
.. thus (you'll have to take my word for it) it puts all digits at the start of the file name into group one, gathers the rest, and replaces all of it with the contents of group #1 (which still contains the first digits, remember?). So the entire file name is replaced with just the digits in front.
If you are thinking "Hey, I can use this", you are not done here. This GREP operation returns a string type, and to convert it to a number you have to tell JS to do so:
n = Number(n);
.. and now you can add 1 to it the usual way. It's also possible your file accidentally does not start with one or more digits, and in that case the variable 'n' will be empty, so you have to test for n = '' before converting to a number.
The GREP is smarter, because it can find any number of digits, which would be a much more difficult task with plain string manipulations, and it automatically rejects (i.e., stops at) the first non-digit.