[mrhoo]

It isn't much more trouble to make sure the first number group
is between 01(or 1) and 12.

var datestring= '02/2014';
var rx=/^(0?[1-9]|1[0-2])[\/-](\d\d(\d\d)?)$/g;

alert(rx.test(datestring));


// The parentheses and /g flag can be used to test the expiration date-

// The parentheses and /g flag can be used to test the expiration date-

var datestring= '10/12';
var rx=/^(0?[1-9]|1[0-2])\D(\d\d(\d\d)?)$/g;


var day= rx.exec(datestring);

if(day){
	var today= new Date(), 
	ty= today.getFullYear(), tm= today.getMonth(),
	y= day[2]- 0;

	if(y<100) y+= 2000;
	alert(y>ty || (y== ty && day[1]-1>= tm))
}
else alert(NaN);