javascript - What is #targetengine? - Stack Overflow

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My only prior experience with #targetengine is when I've used #targetengine "session"; to turn a dialog into a palette when scripting in InDesign. But as I'm trying to figure out how to script a menu, I'm starting to see it pop up being used in other ways and using a term (target?) other than session.

Adobe likes to assume that everyone who wants to script is an experienced programmer sometimes, so I haven't found a clear explanation as to what this is.

So, when I use #targetengine, what am I doing? Can I use any term other than "session"? Some searches suggested this feature has to do with global variables; is that the case? If so, how can I clear them out without restarting InDesign? Is this a JavaScript thing or an ExtendScript/InDesign feature?

My only prior experience with #targetengine is when I've used #targetengine "session"; to turn a dialog into a palette when scripting in InDesign. But as I'm trying to figure out how to script a menu, I'm starting to see it pop up being used in other ways and using a term (target?) other than session.

Adobe likes to assume that everyone who wants to script is an experienced programmer sometimes, so I haven't found a clear explanation as to what this is.

So, when I use #targetengine, what am I doing? Can I use any term other than "session"? Some searches suggested this feature has to do with global variables; is that the case? If so, how can I clear them out without restarting InDesign? Is this a JavaScript thing or an ExtendScript/InDesign feature?

• javascript
• adobe-indesign
• extendscript

Share Improve this question Follow edited Dec 27, 2012 at 21:48 Brendan asked Dec 27, 2012 at 21:43 BrendanBrendan 93811 gold badge1616 silver badges4040 bronze badges 6

• I'm a graphic designer who codes when I need to, not a programmer, so a lot of times I feel like there are assumptions that they make that I just don't know. – Brendan Commented Dec 27, 2012 at 21:48
• I would suggest picking up a book on JavaScript, if that is what you want/need to learn. – Brad Commented Dec 27, 2012 at 21:50
• @Brad, I'm somewhat familiar with JavaScript; I've made web pages for years and have made numerous scripts in InDesign. I'm just trying to expand my skills here and got hung up on this point. JS is really well-documented online usually but because fewer people script for ID, some features are tough to learn about by searching online. Which JavaScript book would help me learn more about #targetengine? – Brendan Commented Dec 27, 2012 at 21:53
• 2 Have you read this, and here? It appears to be a flag to the Javascript engine to keep that variable in the quotes during the entire duration of the time you have InDesign open. It's like a "session"-level value. – Jared Farrish Commented Dec 27, 2012 at 21:55
• @Brendan, Other than the InDesign documentation, I'm not sure. Hopefully someone will come along and have the answer for you. – Brad Commented Dec 27, 2012 at 21:55

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2 Answers 2

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#targetengine is specific to the Adobe scripting in InDesign, PhotoShop, Illustrator etc. - it is not a general Javascript feature.

It specifies how to handle all the global 'stuff' - not only variables but also function declarations and any other change to the global status.

If you use the default 'main' engine all the globals disappear as soon as the script completes. If you use the 'session' engine all the globals are preserved as long as the host application keeps running. This means that if you run the script:

#targetengine "session"

var test = "test";

and later run the script:

#targetengine "session"

alert(test);

you get a message box showing test instead than giving an error

Besides the two standard 'main' and 'session' engines you can create your own ones, with arbitrary names - so if you run the script

#targetengine "mine"

var test = "another test";

and then run

#targetengine "mine"

alert(test);

you get a message box showing another test, but if you run again

#targetengine "session"

alert(test);

you still get test: there are two different 'test' global variables, one in the 'session' engine and one in the (newly created) 'mine' one.

This discussion was brought up in a Slack channel I monitor. One long-time developer said the following (cleaned up a bit for clarity):

As far as I know //@targetengine only works on InDesign (probably including InCopy) and Illustrator.

On InDesign it works properly and on Illustrator it does not. Nevertheless other apps as far as I know all have the ability to use targetengines with C++ and that’s what CEP does with each CEP [extension?] having its own isolated engine.

There are at least 3 types of engine.

1. main engines, in InDesign it’s a temp engine that forgets everything after completing a scripts execution.

2. Public Private engines like session that remember and are active after script execution and good for event listeners. These and main can be identified using $.engineName and found on ESTK / vsCode

3. Private Private $.engineName will show "" can only be created with C++ that what most of the apps use and CEP uses except for InDesign where CEP uses Public Private engines which can be chosen.

He thinks there's also a 4th type he's forgetten.

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