Validate Expiry Date

by Liam Talbot

HTML

<br /><br />
<input type="text" id="expDate" placeholder="MMYY" />
<br /><br />
<input type="button" id="go" value="Test It!" />

JavaScript

function validExpiryDate(value) {
     if (value.length !== 4 || isNaN(value)) {
         return false;
     }

     var mm = parseInt(value.substring(0, 2)),
         yy = parseInt('20' + value.substring(2)),
         thisMonth = (new Date()).getMonth() + 1,
         thisYear = (new Date()).getFullYear();

     if (mm > 12 || mm < 1) {
         return false;
     }

     if (yy < thisYear || (yy === thisYear && mm < thisMonth)) {
         return false;
     }

     return true;
}

$('#go').on('click', function () {
    if (validExpiryDate($('#expDate').val()))
        alert('valid - cool');
    else
        alert('invalid!!!');
});