/**
 *  Look for an active document
 *  without try catch it could produce an error
 *
 */
var doc;
try {
	doc = app.activeDocument; // works with no doc

	var name = doc.name; // this is what throws an error
	alert("You have an active document.");
} catch (error) {
	// error is a variable that contains
	// a message that can be read
	// alert(error);
	alert("You dont have an active document.");
}

var doc = app.documents.add();
var val = 150;
var prefs = doc.documentPreferences;
prefs.pageWidth = val;
prefs.pageHeight = val;

app.documents.add({
	documentPreferences: {
		pageWidth: 150,
		pageHeight: 150,
	},
});

/**
 *  You can create objects with the same structure as
 *   a documents to define values
 *  and than in inject them within a loop
 *  **!Achtung!** This works only in InDesign CS5+
 */

main();
// everyting is in here
function main() {
	var doc_data = {
		documentPreferences: {
			pageWidth: 10,
			pageHeight: 10,
		},
	};
	/*
	now you could do a lot of fancy stuff
	and still have your important data
	like the settings for the doc on the top of the script
	also you could place them into another
	file or something like this.
	*/
	// now loop and create some documents
	var i = 1;
	var num = 13;
	var arr = new Array();

	while (i < num) {
		// do something fancy here
		doc_data.documentPreferences.pageWidth += 10;
		doc_data.documentPreferences.pageHeight += 10;
		// now push it into an array
		arr.push(app.documents.add(doc_data));
		i++;
	}

	// add some text. just for fun
	add_text(arr);
}

/**
 *  This function adds text to an doc
 *  it takes an array of documents as argument
 */
function add_text(arr) {
	for (var j in arr) {
		var d = arr[j];
		var pw = d.documentPreferences.pageWidth;
		var ph = d.documentPreferences.pageHeight;
		var gutter = pw / 10;
		var gb = [gutter, gutter, ph - gutter, pw - gutter];
		var pg = d.pages.item(0);
		pg.textFrames.add({
			geometricBounds: gb,
			contents: "I'm doc number " + j,
		});
	}
}

app.documents.everyItem().revert();

// Like Uncle Ben saz: "With great power comes great responsibility!"
app.documents.everyItem().close(SaveOptions.NO);