Draw gridlines in a Titanium window

app.js

// implement like this:
var window = Ti.UI.createWindow({
	backgroundColor:'#fff'
});
// draw the gridlines first so your other elements stack on top of them
// without requiring you to set the z-index property of each
var grid = require('gridlines');
grid.drawgrid(10,window);

gridlines.js

exports.drawgrid = function(gridspacing, win, color) {
	// gridspacing = integer
	// win = window to which the grid will be added
	// color = optional color for lines
	var clr = (color) ? color : '#dedede';
	var numhoriz = Math.ceil(Ti.Platform.displayCaps.platformHeight / gridspacing);
	var numvert = Math.ceil(Ti.Platform.displayCaps.platformWidth / gridspacing);
	for(h=0; h<numhoriz;h++) {
		var hline = Ti.UI.createView({
			height:1,
			width:'100%',
			backgroundColor:clr,
			top: h*gridspacing,
			left:0
		});
		win.add(hline);
	}
	for(v=0; v<numvert;v++) {
		var vline = Ti.UI.createView({
			width:1,
			height:'100%',
			backgroundColor:clr,
			left: v*gridspacing,
			top:0
		});
		win.add(vline);
	}
}

I'm new to Titanium. Need help.
I put gridlines.js to controllers folder of my new app, then in index.js put two lines:
var grid = require('gridlines');
grid.drawgrid(20,win);
Try to run and got the error: Script Error Couldn't find module: gridlines.
What I'm doing wrong?

Just to possibly leave some info here - as I understand gridlines.js should go into your alloy apps lib folder and not into the controllers folder.