Ported to Node.js + FFI from: http://raspberrycompote.blogspot.com/2012/12/low-level-graphics-on-raspberry-pi-part_9509.html

screen_info.js

const fs = require('fs');
const ffi = require('ffi');
const ref = require('ref');
const Struct = require('ref-struct');
const ArrayType = require('ref-array');

const ioctl = ffi.ForeignFunction(
  ffi.DynamicLibrary().get('ioctl'),
  'int', ['int', 'int', 'void*']
);

// #typedefs
const __u32 = ref.types.uint32;

// from <linux/fb.h>
const FBIOGET_VSCREENINFO = 0x4600;
const fb_bitfield = Struct([
	[__u32, 'offset'],			/* beginning of bitfield	*/
	[__u32, 'length'],			/* length of bitfield		*/
	[__u32, 'msb_right']		/* != 0 : Most significant bit is */
					/* right */
]);
const fb_var_screeninfo = Struct([
	[__u32, 'xres'],			/* visible resolution		*/
	[__u32, 'yres'],
	[__u32, 'xres_virtual'],		/* virtual resolution		*/
	[__u32, 'yres_virtual'],
	[__u32, 'xoffset'],			/* offset from virtual to visible */
	[__u32, 'yoffset'],			/* resolution			*/

	[__u32, 'bits_per_pixel'],		/* guess what			*/
	[__u32, 'grayscale'],		/* != 0 Graylevels instead of colors */

	[fb_bitfield, 'red'],		/* bitfield in fb mem if true color, */
	[fb_bitfield, 'green'],	/* else only length is significant */
	[fb_bitfield, 'blue'],
	[fb_bitfield, 'transp'],	/* transparency			*/

	[__u32, 'nonstd'],			/* != 0 Non standard pixel format */

	[__u32, 'activate'],			/* see FB_ACTIVATE_*		*/

	[__u32, 'height'],			/* height of picture in mm    */
	[__u32, 'width'],			/* width of picture in mm     */

	[__u32, 'accel_flags'],		/* (OBSOLETE) see fb_info.flags */

	/* Timing: All values in pixclocks, except pixclock (of course) */
	[__u32, 'pixclock'],			/* pixel clock in ps (pico seconds) */
	[__u32, 'left_margin'],		/* time from sync to picture	*/
	[__u32, 'right_margin'],		/* time from picture to sync	*/
	[__u32, 'upper_margin'],		/* time from sync to picture	*/
	[__u32, 'lower_margin'],
	[__u32, 'hsync_len'],		/* length of horizontal sync	*/
	[__u32, 'vsync_len'],		/* length of vertical sync	*/
	[__u32, 'sync'],			/* see FB_SYNC_*		*/
	[__u32, 'vmode'],			/* see FB_VMODE_*		*/
	[__u32, 'rotate'],			/* angle we rotate counter clockwise */
	[ArrayType(__u32, 5), 'reserved']		/* Reserved for future compatibility */
]);

// Open the framebuffer device file for reading and writing
const fbfd = fs.openSync('/dev/fb0', 'w+');
console.log('The framebuffer device opened: fd=%d', fbfd);

// Get variable screen information
const var_info = new fb_var_screeninfo();

if (ioctl(fbfd, FBIOGET_VSCREENINFO, var_info.ref())) {
  console.log("Error reading variable screen info.");
}

console.log("Display info %dx%d, %d bpp",
             var_info.xres, var_info.yres,
             var_info.bits_per_pixel );

// close file
fs.closeSync(fbfd);