In a high-volume data-entry environment, where productivity is measured in opera- tors’ keystrokes and time spent per form, you want to build more intelligence in a form. For example, you want to allow two-digit year entries, but code the validation routine so that it fills the field with the expanded version of the date because the backend data…

Enhanced date validation function.js

function checkDate(fld) {
 var mo, day, yr;
 var entry = fld.value;
 var reLong = /\b\d{1,2}[\/-]\d{1,2}[\/-]\d{4}\b/;
 var reShort = /\b\d{1,2}[\/-]\d{1,2}[\/-]\d{2}\b/;
 var valid = (reLong.test(entry)) || (reShort.test(entry));
 if (valid) {
 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);
 // handle two-digit year
 if (yr < 100) {
 var today = new Date( );
 // get current century floor (e.g., 2000)
 var currCent = parseInt(today.getFullYear( ) / 100) * 100;
 // two digits up to this year + 15 expands to current century
 var threshold = (today.getFullYear( ) + 15) - currCent;
 if (yr > threshold) {
 yr += currCent - 100;
 } else {
 yr += currCent; }
 }
 var testDate = new Date(yr, mo-1, day);
 if (testDate.getDate( ) == day) {
 if (testDate.getMonth( ) + 1 == mo) {
 if (testDate.getFullYear( ) == yr) {

// fill field with database-friendly format
 fld.value = mo + "/" + day + "/" + 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;
}