a script which allows one to create a grid (margins, rows, and columns) in illustrator similar to "create guides..." in indesign.

CreateGrid_0_0.js

/**
 *	Create Grid
 *
 *	Ken Frederick
 *	ken.frederick@gmx.de
 *
 *	http://cargocollective.com/kenfrederick/
 *	http://kenfrederick.blogspot.com/
 *
 */


// ------------------------------------------------------------------------
// Properties
// ------------------------------------------------------------------------

/**
 *	Note from the Scriptographer.org Team
 *	
 *	In Scriptographer 2.9, we switched to a top-down coordinate system and
 *	degrees for angle units as an easier alternative to radians.
 *	
 *	For backward compatibility we offer the possibility to still use the old
 *	bottom-up coordinate system and radians for angle units, by setting the two
 *	values bellow. Read more about this transition on our website:
 *	http://scriptographer.org/news/version-2.9.064-arrived/
 */

script.coordinateSystem = 'bottom-up';
script.angleUnits = 'radians';


// document properties
var sel;
var group;
var groupMargins;
var groupRowsCols;
var palette;


// conversions
var ptToMm = 0.352777778;
var mmToPt = 2.83464567;

var ptToIn = 0.0138888889;
var inToPt = 72;

var ptToPi = 0.0833333333;
var piToPt = 12;


// default unit of measure
var unit = 'millimeter';
var valDef = 6*mmToPt;


// values
var values = {
	// ------------------------------------
	// margins
	// ------------------------------------
	marginTop:		valDef,
	marginBottom:	valDef,
	marginLeft:		valDef,
	marginRight:	valDef,


	// ------------------------------------
	// rows
	// ------------------------------------
	rows:			0,
	rowGutter:		valDef,


	// ------------------------------------
	// cols
	// ------------------------------------
	cols:			0,
	colGutter:		valDef,


	// ------------------------------------
	// options
	// ------------------------------------
	bRemoveExist:	false,
	bAllArtboards:	true
};


// gui components
var components = {
	// ------------------------------------
	// flyout menu
	// ------------------------------------
	bMmUnit: {
		type:		'menu-entry',
		value:		'millimeter',
		onSelect: function() {
			unit = 'millimeter';
			valDef = 6*mmToPt;
			updatePalette(unit, valDef);
		}
	},
	bInUnit: {
		type:		'menu-entry',
		value:		'inch',
		onSelect: function() {
			unit = 'inch';
			valDef = 0.5*inToPt;
			updatePalette(unit, valDef);
		}
	},
	bPiUnit: {
		type:		'menu-entry',
		value:		'pica',
		onSelect: function() {
			unit = 'pica';
			valDef = 3*piToPt;
			updatePalette(unit, valDef);
		}
	},
	bPtUnit: {
		type:		'menu-entry',
		value:		'point/pixel',
		onSelect: function() {
			unit = 'point';
			valDef = 36;
			updatePalette(unit, valDef);
		}
	},
	
	
	// ------------------------------------
	// margins
	// ------------------------------------
	marginRule: { 
		type: 			'ruler',
		label: 			'Margins',
		fullSize: 		true,
	},

	marginTop: {
		type:			'number',
		label:			'Top',
		units:			unit,
		steppers:		true,
		fractionDigits:	2,
	},
	marginBottom: {
		type:			'number',
		label:			'Bottom',
		units:			unit,
		steppers:		true,
		fractionDigits:	2,
	},
	marginLeft: {
		type:			'number',
		label:			'Left',
		units:			unit,
		steppers:		true,
		fractionDigits:	2,
	},
	marginRight: {
		type:			'number',
		label:			'Right',
		units:			unit,
		steppers:		true,
		fractionDigits:	2,
	},
	
	// ------------------------------------
	// rows
	// ------------------------------------
	rowRule: { 
		type: 			'ruler',
		label: 			'Rows',
		fullSize: 		true,
	},
	
	rows: {
		type:			'number',
		label:			'Number',
		units:			'none',
		fractionDigits:	0,
	},
	rowGutter: {
		type:			'number',
		label:			'Gutter',
		units:			unit,
		fractionDigits:	2,
	},
	
	
	// ------------------------------------
	// cols
	// ------------------------------------
	colRule: { 
		type: 			'ruler',
		label: 			'Columns',
		fullSize: 		true,
	},
	
	cols: {
		type:			'number',
		label:			'Number',
		units:			'none',
		fractionDigits:	0,
	},
	colGutter: {
		type:			'number',
		label:			'Gutter',
		units:			unit,
		fractionDigits:	2,
	},	
	
	
	// ------------------------------------
	// options
	// ------------------------------------
	optionsRule: { 
		type: 			'ruler',
		label: 			'Options',
		fullSize: 		true,
	},

	bRemoveExist: {
		type:		'checkbox',
		label:		'Remove Existing\nMargins/Grid',
	},

	bAllArtboards: {
		type:		'checkbox',
		label:		'All Artboards',
	},


	// ------------------------------------
	// apply that shit!
	// ------------------------------------
	applyRule: { 
		type: 			'ruler',
		fullSize: 		true,
	},

	submit: { 
		type: 'button', 
		value: 'Generate',
		fullSize: true,
		onClick: function() {
			Main();
		}
	}

};



// ------------------------------------------------------------------------
// Setup
// ------------------------------------------------------------------------
function Setup() {
	// initialize the palette window
	palette = new Palette('Create Grid', components, values);
}



// ------------------------------------------------------------------------
// Update
// ------------------------------------------------------------------------
function Update() {
}



// ------------------------------------------------------------------------
// Main
// ------------------------------------------------------------------------
function Main() {
	// create grid layer
	var layer;
	for(i in activeDocument.layers) {
		var l = activeDocument.layers[i];
		l.locked = false;

		if(l.name == '_grid_') {
			layer = l;
			if(values.bRemoveExist) {
				for(j in l.children) {
					if(l.children[j].name == '_created_grid_') l.children[j].remove();
				}
			}
			//break;
		}
		
	}
	if(layer == null) {
		layer = new Layer();
		layer.name = '_grid_';
	}


	// create guides
	var theArtboard;
	group = new Group();
	group.name = '_created_grid_';

	if(values.bAllArtboards) {
		// across all artboards
		for(i in activeDocument.artboards) {
			//print('all artboards', i);
			theArtboard = activeDocument.artboards[i];
			group.appendTop( createMargins(theArtboard) );
			group.appendTop( createRowsCols(theArtboard) );
		}
	} else {
		theArtboard = activeDocument.activeArtboard;
		// active artboard
		group.appendTop( createMargins(theArtboard) );
		group.appendTop( createRowsCols(theArtboard) );
	}
	layer.appendTop(group);
	layer.locked = true;
}



// ------------------------------------------------------------------------
// methods
// ------------------------------------------------------------------------
function createMargins(theArtboard) {
	var bounds = theArtboard.bounds;
	var active = activeDocument.activeArtboard;

	var bw = bounds.width;
	var bh = bounds.height;
	var bx = bounds.x - active.bounds.x;
	var by = bounds.y - active.bounds.y; 


	// ------------------------------------
	// create margins
	// ------------------------------------

	groupMargins = new Group();


	/**
	 * top & bottom margins
	 */
	var mTop	= new Path.Line( new Point(bx, by+(bh-values.marginTop)), new Point(bx+bw, by+(bh-values.marginTop)) );
	mTop.guide = true;
	groupMargins.appendTop(mTop);
	
	var mBottom	= new Path.Line( new Point(bx, by+values.marginBottom), new Point(bx+bw, by+values.marginBottom) );
	mBottom.guide = true;
	groupMargins.appendTop(mBottom);


	/**
	 * left & right margins
	 */
	var mLeft	= new Path.Line( new Point(bx+values.marginLeft, by), new Point(bx+values.marginLeft, by+bh) );
	mLeft.guide = true;
	groupMargins.appendTop(mLeft);

	var mRight	= new Path.Line( new Point(bx+(bw-values.marginRight), by), new Point(bx+(bw-values.marginRight), by+bh) );
	mRight.guide = true;
	groupMargins.appendTop(mRight);

	return groupMargins;
}


// ------------------------------------------------------------------------
function createRowsCols(theArtboard) {
	var bounds = theArtboard.bounds;
	var active = activeDocument.activeArtboard;

	var bw = bounds.width;
	var bh = bounds.height;
	var bx = bounds.x - active.bounds.x;
	var by = bounds.y - active.bounds.y; 
	var activeSpace = new Point( bw-(values.marginLeft+values.marginRight), bh-(values.marginTop+values.marginBottom) );


	// ------------------------------------
	// create columns & rows
	// ------------------------------------
	groupRowsCols = new Group();


	/**
	 * cols
	 */
	if( values.cols > 0 ) {
		var colGutterCombined = Math.abs( values.colGutter*(values.cols-1) );
		activeSpace.x -= colGutterCombined;
		activeSpace.x /= values.cols;
	
		var x = values.marginLeft;
		for(var i=0; i<values.cols-1; i++) {
			x += activeSpace.x;
			var gutterLeft = new Path.Line( new Point(bx+x, by), new Point(bx+x,by+bh) );
			gutterLeft.guide = true;
			groupRowsCols.appendTop(gutterLeft);

			x += values.colGutter;
			var gutterRight = new Path.Line( new Point(bx+x, by), new Point(bx+x,by+bh) );
			gutterRight.guide = true;
			groupRowsCols.appendTop(gutterRight);
		}
	}	
	

	/**
	 * rows
	 */
	if( values.rows > 0 ) {
		var rowGutterCombined = Math.abs( values.rowGutter*(values.rows-1) );
		activeSpace.y -= rowGutterCombined;
		activeSpace.y /= values.rows;
	
		var y = values.marginTop;
		for(var i=0; i<values.rows-1; i++) {
			y += activeSpace.y;
			var gutterTop = new Path.Line( new Point(bx, by+y), new Point(bx+bw, by+y) );
			gutterTop.guide = true;
			groupRowsCols.appendTop(gutterTop);

			y += values.rowGutter;
			var gutterBottom = new Path.Line( new Point(bx, by+y), new Point(bx+bw, by+y) );
			gutterBottom.guide = true;
			groupRowsCols.appendTop(gutterBottom);
		}
	}

	return groupRowsCols;
}


// ------------------------------------------------------------------------
function roundDecimal(orig,deci) {
	var multi = Math.pow(10,deci);
	var num = Math.round(orig * multi)/multi;
	return num;
}


// ------------------------------------------------------------------------
function updatePalette(theUnit, theValDef) {
	// print('unit', theUnit);
	// print('val', theValDef);

	// unit
	palette.getComponent('marginTop').units = theUnit;
	palette.getComponent('marginBottom').units = theUnit;
	palette.getComponent('marginLeft').units = theUnit;
	palette.getComponent('marginRight').units = theUnit;

	palette.getComponent('rowGutter').units = theUnit;
	palette.getComponent('colGutter').units = theUnit;

	// value
	palette.getComponent('marginTop').value = theValDef;
	palette.getComponent('marginBottom').value = theValDef;
	palette.getComponent('marginLeft').value = theValDef;
	palette.getComponent('marginRight').value = theValDef;

	palette.getComponent('rowGutter').value = theValDef;
	palette.getComponent('colGutter').value = theValDef;

	// reset
	//palette.reset();
}



// ------------------------------------------------------------------------
// Execution
// ------------------------------------------------------------------------
Setup();
Update();
//Main();

Dear @frederickk is this script still supposed to work in AI CC2019? I get an error. As I am not a developer and just have basic knowledge of scripts through the use in InDesign, changing the line 29 to “top-down” does not make it work.