<p>I saw a potential answer here but that was for YYYY-MM-DD: <a href="http://paulschreiber.com/blog/2007/03/02/javascript-date-validation/" rel="noreferrer">JavaScript date validation</a></p>

<p>I modified the code code above for MM-DD-YYYY like so but I still can't get it to work:</p>

<pre><code>String.prototype.isValidDate = function() 
{
     var IsoDateRe = new RegExp("^([0-9]{2})-([0-9]{2})-([0-9]{4})$");
     var matches = IsoDateRe.exec(this);
     if (!matches) return false;
     var composedDate = new Date(matches[3], (matches[1] - 1), matches[2]);
     return ((composedDate.getMonth() == (matches[1] - 1)) &amp;&amp;
      (composedDate.getDate() == matches[2]) &amp;&amp;
      (composedDate.getFullYear() == matches[3]));
}
</code></pre>

<p>How can I get the above code to work for MM-DD-YYYY and better yet MM/DD/YYYY?</p>

<p>Thanks.</p>

You can simplify it somewhat by changing the first two lines of the function to this:
```
```
var matches = this.match(/^([0-9]{2})\/([0-9]{2})\/([0-9]{4})$/);
```
```
Or, just change the parameter to the RegExp constructor to be
```
```
^([0-9]{2})\/([0-9]{2})\/([0-9]{4})$
```
```