Q:

Dropdown undefined javascript form validation error

I have the following sample of html code:
<form id="registration" action="process.php" onsubmit="return validateForm()" method="post">
    <label for="range_date" class="form">Select Range Date</a></label>
    <select name="range_date">
        <option value="" style="display:none;"></option>
        <option value="June 27th 2014 6:00pm">June 27th 2014 6:00pm</option>
        <option value="June 27th 2014 8:00pm">June 27th 2014 8:00pm</option>
    </select>
</form >

And the following sample js code:
if (document.forms["registration"]["range_date"] != 'undefined') 
{
    var range_date=document.forms["registration"]["range_date"].value;
    if (range_date==null || range_date=="")
    {  
        alert("Please select a Range Date");
        return false;
    }  
}

I get an error in firebug stating: "document.forms.registration.range_date is undefined" but I don't expect it to reach the inside of the if statement. Any thoughts?

A:

That is because 'undefined' != undefined. 
Just use a truthy check
if (document.forms["registration"]["range_date"]) {

or drop the quotes
if (document.forms["registration"]["range_date"]===undefined) {

