Is it possible to execute JSX scripts from outside ExtendScript?

For Windows users, you can use a vbs script. Pass arguments to the .jsx script by providing arguments to the cscript command like so: cscript test.vbs "hello". test.vbs could look like so:

Dim appRef
Dim javaScriptFile
Dim argsArr()

Dim fsObj : Set fsObj = CreateObject("Scripting.FileSystemObject")
Dim jsxFile : Set jsxFile = fsObj.OpenTextFile("C:\Users\path\test.jsx", 1, False)
Dim fileContents : fileContents = jsxFile.ReadAll
jsxFile.Close
Set jsxFile = Nothing
Set fsObj = Nothing

javascriptFile = fileContents & "main(arguments);"

Set appRef = CreateObject("Illustrator.Application")

ReDim argsArr(Wscript.Arguments.length-1)

For i = 0 To Wscript.Arguments.length-1
    argsArr(i) = Wscript.Arguments(i)
Next

Wscript.Echo appRef.DoJavaScript(javascriptFile, argsArr, 1)

The Wscript.Echo will return the last line returned by the .jsx file. A .jsx file example could be:

function main(argv) {
    alert(argv[0]);
    return "test";
}

When ran, you should seee Illustrator (or whatever adobe program) alert "hello" and then "test" will be returned to stdout (you should see it in the command prompt window).

Are you on a Mac? If so, you can use AppleScript with the osascript tool to execute your JavaScript. Here are some examples:

Running JSX and Returning a Value

Save this as ~/temp/foo.scpt:

tell application "Adobe Illustrator"
     -- 'do javascript' runs any arbitrary JS.
     -- We're using the #include feature to run another
     -- file. (That's an Adobe extension to JS.)
     --
     -- You have to pass a full, absolute path to #include.
     --
     -- The documentation alleges that 'do javascript'
     -- can be passed an AppleScript file object, but
     -- I wasn't able to get that to work.
     do javascript "#include ~/temp/foo.jsx"
end tell

And save this as ~/temp/foo.jsx:

var doc = app.activeDocument;
var numLayers = doc.layers.length;

// The last value in the JSX file will be printed out by
// osascript. 
numLayers;

Now, from the command line run osascript ~/temp/foo.scpt It will print the number of layers in the active Illustrator document.

Getting data out of the JavaScript is limiting. You can't print to stdout from within the JavaScript. Instead, place the value you want to return as the last statement of the JSX file; it will be printed by osascript. (Here's why: The last value in the JSX file is the return value of the do javascript AppleScript statement. That is also the last value in the AppleScript file, and osascript prints the final value.)

The value you return from JavaScript can be a number, a string, an array, or anything else that retains its value when converted to a string. If you want to return a complex object, you'll need to #include a JSON library and call .toJSONString() on the object.

Passing Arguments to JSX

To pass arguments to the JSX code, follow this example:

File ~/temp/args.scpt:

on run argv
    tell application "Adobe Illustrator"
        set js to "#include '~/temp/args.jsx';" & return
        set js to js & "main(arguments);" & return
        do javascript js with arguments argv
    end tell
end run

File ~/temp/args.jsx

function main(argv) {
    var layer = app.activeDocument.activeLayer;
    app.defaultStroked = true; 
    app.defaultFilled = true;

    // Top, left, width, height (in points).
    // Note that parameters start at argv[0].
    layer.pathItems.rectangle(argv[0], argv[1], argv[2], argv[3]);
}

And then run osascript args.scpt 50 30 10 80

Debugging

The do javascript command also has options for launching the ExtendScript debugger. For details, open the Illustrator dictionary in AppleScript Editor.