The Adobe Fireworks JavaScript engine has an undocumented File class that has some useful features lacking in the documented Files object.

gistfile1.js

// to access a file, create a new instance of the File class by passing in 
// a standard OS-style path to the constructor.  I've only tested this on
// Windows, but a standard path on OS X should work, too. 

var f = new File("C:\\test.txt"); 

// unlike the file references created by the Files object, these have some
// useful properties, like length, which is the file size in bytes

console.log(f.length);

// modification is the last modified date of the file, but it appears to
// have a bug, where the date is a month newer than it should be.  this 
// function would return the corrected date.

function getModifiedDate(
  inFile)
{
	var date = new Date(inFile.modified.getTime());

	if (date.getMonth() == 0) {
		date.setFullYear(date.getFullYear() - 1);
	}

	date.setMonth((date.getMonth() - 1 + 12) % 12);

	return date;
}

console.log(getModifiedDate(f));