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; }
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 database requires it. Moreover, the two-digit entry needs to be done in a maintenance-free way so that the range of allowable years for two-digit dates contin- ues to modify itself as the years progress.

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