JavaScript で月の違いを計算するにはどうすればよいですか?

function monthDiff(d1, d2) {
    var months = (d2.getFullYear() - d1.getFullYear()) * 12;
    months -= d1.getMonth();
    months += d2.getMonth();
    return months <= 0 ? 0 : months;
}

// November 4th, 2008, to March 12th, 2010
console.log(monthDiff(new Date(2008, 10, 4), new Date(2010, 2, 12))); // Output: 16

// January 1st, 2010, to March 12th, 2010
console.log(monthDiff(new Date(2010, 0, 1), new Date(2010, 2, 12))); // Output: 2

// February 1st, 2010, to March 12th, 2010
console.log(monthDiff(new Date(2010, 1, 1), new Date(2010, 2, 12))); // Output: 1