使用javascript验证日期？

Question

In Javascript I am trying to write the validation for a date, where the user has to select a future date and not a past date. My code seems to work only when I use a date from last month (eg 26/11/2011 ). This is my script:

<script type="text/javascript" >
   function mydate()
   {           
       var d= new Date ();
       var day= d.getDate ();

       var mon=d.getMonth ();

       var year= d.getFullYear ();

       var dateformat= day+"/"+mon+"/"+year ;

       var get= document.getElementById("txt").value; 

       if(get >= dateformat )
       {
          alert ('yes valid');
       }
       else 
       {
            alert('Date should greater than to date ');
       }
   }
</script> 

Answer 1

You are comparing the date values as strings. This is a textual comparison not a date-wise comparison so it will pretty much never work except by coincidence. You need to parse the date value the user enters into a Date data type and do a comparison that way.

Whenever possible you should avoid writing date manipulation code yourself and try to leverage a known working solution, eg the jQuery UI Datepicker .