The checkDate( ) validation function in Example 2-3 assumes that users will enter dates in either mm/dd/yyyy or mm-dd-yyyy formats (in that order only), and that the validation must test for the entry of a true date. There is no boundary checking here, so practically any year is accepted. As a form-validation function, this one takes a ref- eren…

checkDate().js

function checkDate(fld) {
 var mo, day, yr;
 var entry = fld.value;
 var re = /\b\d{1,2}[\/-]\d{1,2}[\/-]\d{4}\b/;
 if (re.test(entry)) {
 var delimChar = (entry.indexOf("/") != -1) ? "/" : "-";
 var delim1 = entry.indexOf(delimChar);
 var delim2 = entry.lastIndexOf(delimChar);
 mo = parseInt(entry.substring(0, delim1), 10);
 day = parseInt(entry.substring(delim1+1, delim2), 10);
 yr = parseInt(entry.substring(delim2+1), 10);
 var testDate = new Date(yr, mo-1, day);
 if (testDate.getDate( ) == day) {
 if (testDate.getMonth( ) + 1 == mo) {
 if (testDate.getFullYear( ) == yr) {
 return true;
 } else {
 alert("There is a problem with the year entry.");
 }
 } else {
 alert("There is a problem with the month entry.");
 }
 } else {
 alert("There is a problem with the date entry.");
 }
 } else {
 alert("Incorrect date format. Enter as mm/dd/yyyy.");
 }
 return false;
}