JavaScript Detecting Valid Dates

Question

Possible Duplicate:
Detecting an “invalid date” Date instance in JavaScript

I was using the following to detect a valid date:

var text = $('#Date').val(); var date = Date.parse(text);  if (isNaN(date)) {       // Invalid date } 

But found that Date.parse thinks the following are valid dates (mm/dd/yyyy)

• 2/30/2011
• 11/31/2011

Any other way to detect invalid dates when the number of days surpasses the total number of days in the month?

UPDATE: An even larger problem is that the jQuery validation plugin doesn't detect this as an invalid date either!

SOLUTION:

Based on @Guffa's comments I have created the following function to validate dates:

function validDate(text) {      var date = Date.parse(text);      if (isNaN(date)) {         return false;     }      var comp = text.split('/');      if (comp.length !== 3) {         return false;     }      var m = parseInt(comp[0], 10);     var d = parseInt(comp[1], 10);     var y = parseInt(comp[2], 10);     var date = new Date(y, m - 1, d);     return (date.getFullYear() == y && date.getMonth() + 1 == m && date.getDate() == d); } 

Answer 1

To check if a date is valid you can parse the components of the date, create a Date object from it, and check if the components in the data is the same as the parsed components. If you create a Date object from compnents that are out of range, the values will flow over to the next/previous period to create a valid date.

For example, new Date(2011,0,42) will create an object that contains the date 2/11/2011 instead of 1/42/2011.

By parsing the components instead of the full date you will also get around the problem with different date formats. My browser will for example expect a date format like y-m-d rather than d/m/y.

Example:

var text = '2/30/2011'; var comp = text.split('/'); var m = parseInt(comp[0], 10); var d = parseInt(comp[1], 10); var y = parseInt(comp[2], 10); var date = new Date(y,m-1,d); if (date.getFullYear() == y && date.getMonth() + 1 == m && date.getDate() == d) {   alert('Valid date'); } else {   alert('Invalid date'); } 

Demo: http://jsfiddle.net/Guffa/UeQAK/