RandomSelection.jsx

/**
Script © 2022 Boris Boguslavsky
https://github.com/borisboguslavsky

Based on the Random Selection Functionality from the Randomill Illustrator Plugin
https://randomill.com/

Please note:

It may take some time to run the script on large sets of objects. This is because of the fact that the core of this script works by flipping the `.selected` flag of objects within Illustrator via ExtendScript. This necessarily means that Illustrator redraws the whole screen every time a single object has its `.selected` flag modified. It's an unfortunate limitation of how Adobe has implemented this particular feature within ExtendScript. 

This script is a stripped-down version of Randomill's (https://randomill.com/) random select function.

The main difference between the two is that the full version of this function within Randomill has an 'experimental' fast-select mode that circumvents the above speed limitation by creating an executing an action dynamically instead of iterating over objects and flipping their `.selected` flags. This means that random selection can happen almost instantaneously, regardless of how large the initial set of objects is.

Feel free to modify this script as you see fit. I hope you find it useful.
*/

var SCRIPT_NAME = "Randomill Select"

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var mainPanelWindow = new Window('dialog', 'Random Selection \u00A9 randomill.com', undefined);
	mainPanelWindow.orientation = 'column';
	mainPanelWindow.alignChildren = ['fill', 'fill'];
// Radios for selection method
var selectionMethodSelect = mainPanelWindow.add('panel', undefined, 'Selection Method:');
	selectionMethodSelect.orientation = 'column';
	selectionMethodSelect.alignChildren = ['fill', 'fill'];
	var selMethodPercentageRadio = selectionMethodSelect.add('radiobutton', undefined, 'Percentage');
	var selMethodCountRadio = selectionMethodSelect.add('radiobutton', undefined, 'Count');
	selMethodPercentageRadio.value = true; // percentage method is selected by default
// Text field for entering desired value
var valueInputTextField = mainPanelWindow.add('panel', undefined, 'Value:');
	valueInputTextField.orientation = 'row';
	valueInputTextField.alignChildren = ['fill', 'fill'];
	var selectionValue = valueInputTextField.add('edittext', undefined, 50);
	// selectionValue.minimumSize = [1, undefined];
	// selectionValue.active = true;
// OK and Cancel Buttons
var cancelAndOkButtons = mainPanelWindow.add('group');
	cancelAndOkButtons.alignChildren = ['fill', 'fill'];
	cancelAndOkButtons.margins = [0, 0, 0, 0];
	var cancel = cancelAndOkButtons.add('button', undefined, 'Cancel');
		cancel.helpTip = 'Press Esc to Close';
		cancel.onClick = function () { 
			mainPanelWindow.close(); 
		}
	var ok = cancelAndOkButtons.add('button', undefined, 'OK');
		ok.helpTip = 'Press Enter to Run';
		ok.onClick = function () {
			randomizeSelection();
			mainPanelWindow.close();
		}
		ok.active = true;



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function randomizeSelection() {
	// Ensure there's an active document
	if (app.documents.length === 0) {
		alert("Error: No currently active document.");
		mainPanelWindow.close();
		return;
	}

	var objects = app.activeDocument.selection;

	// Ensure there's at least two objects in the selection
	if (objects.length < 2) {
		alert("Error: Please select at least two items. If more than two items are selected, make sure they're ungrouped.");
		return;
	}

	// Establish the selection method
	var selectionMethod = selMethodPercentageRadio.value ? 'percentage' : 'count';

	// Make sure the entered value is valid
	var value = parseFloat(selectionValue.text)
	if (isNaN(value)) {
		alert('Error: Could not parse entered value.');
		return;
	}

	// Determine the number of objects that should end up selected
	var numberOfObjectsInFinalSelection = calculateNumberOfObjectsToSelect(objects.length, selectionMethod, value);

	// If the number of objects calculated ends up being zero, deslect everything
	if (numberOfObjectsInFinalSelection <= 0) { 
		app.activeDocument.selection = [];
		return;
	}

	// If the number of objects to select is somehow greater than the selection length, just return
	if (numberOfObjectsInFinalSelection >= objects.length) {
		return;
	}

	// Determine whether the most efficient way is to select objects starting from an empty array,
	// or to deslect objects from the currently selected object array
	var whatToDo = selectOrDeselect(objects.length, numberOfObjectsInFinalSelection);
	var deselect = whatToDo.deselect;
	
	// How many objects must be either selected or deselected?
	var howManyTimes = whatToDo.number;

	// Create a randomized array of indices with the length of the current selection
	var selectionIndexList = randomizedIndexListFischerYates(objects.length);
	
	// If selecting instead of deselecting, start with an empty array
	if (!deselect) app.activeDocument.selection = [];

	// Set selection by modifying each object's 'selected' attribute
	for (i = 0; i < howManyTimes; i++) {
		var j = selectionIndexList[i];
		if (objects[j] !== undefined) {
			objects[j].selected = !deselect;
		};
	};

	return;
	
}


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function calculateNumberOfObjectsToSelect(selectionLength, selectionMethod, value) {
	
	var numberOfObjectsToSelect = selectionMethod === 'percentage' 
		? Math.round(selectionLength * value / 100)
		: value

	$.writeln('	Number of objects to select: ' + numberOfObjectsToSelect)

	if (numberOfObjectsToSelect <= 0) return 0;
	if (numberOfObjectsToSelect >= selectionLength) return selectionLength;

	return numberOfObjectsToSelect;
}

function selectOrDeselect(selectionLength, numObjToSelect) {
	var deselect = false;
	var modeTippingPoint = 0.6;
	var remainingSelectionPercentage = numObjToSelect / selectionLength;
	if (remainingSelectionPercentage <= modeTippingPoint) {
		// Select
		var numberOfItemsToOperateOn = numObjToSelect
		$.writeln('	Select ' + numberOfItemsToOperateOn + ' objects')
	} else {
		// Deselect
		var numberOfItemsToOperateOn = selectionLength - numObjToSelect
		deselect = true;
		$.writeln('	Deselect ' + numberOfItemsToOperateOn + ' objects')
	}

	return { deselect: deselect, number: numberOfItemsToOperateOn };
}

function shuffleArray(array) {
	var curId = array.length;
	// There remain elements to shuffle
	while (0 !== curId) {
		// Pick a remaining element
		var randId = Math.floor(Math.random() * curId);
		curId -= 1;
		// Swap it with the current element.
		var tmp = array[curId];
		array[curId] = array[randId];
		array[randId] = tmp;
	}
	return array;
}

function randomizedIndexListFischerYates(length) {
	// Create an unshuffled array
	var randomizedArray = new Array();
	for (var i=0; i < length; i++) {
		randomizedArray.push(i);
	}
	// Shuffle the array using fischer-yates
	return shuffleArray(randomizedArray);
}

// Show script UI when script is run
mainPanelWindow.center();
mainPanelWindow.show();