If your date is not in format standar yyyy-mm-dd (2017-02-06) for example 20/06/2016. You can use this code
var parts ='01/07/2016'.val().split('/');
var d1 = Number(parts[2] + parts[1] + parts[0]);
parts ='20/06/2016'.val().split('/');
var d2 = Number(parts[2] + parts[1] + parts[0]);
return d1 > d2