Why is this javascript validation not working for the selectlist

Question

The javascript should be checking to see if the user didn't select anything in a select list if the value is the first option which is "Please choose a seminar". It appears to just ignore the script.

<apex:page controller="vfCnt_chooseSeminar" >

<apex:form > 

<apex:PageBlock title="Choose Your Preferred Seminar(s) for {!progName}">

            <apex:pageBlockButtons >
                <apex:commandButton action="{!saveItem}" value="Next"/>
                <apex:commandButton onclick="validateFunction('{!$Component.first}')" action="{!cancelAction}" value="Cancel"/>
            </apex:pageBlockButtons>

            <h1>First Preference:</h1><p />
                   <apex:selectList id="first" value="{!semName1}" multiselect="false" size="1">
                   <apex:selectOptions value="{!items}"/>
                   </apex:selectList>
            <p />
                    <h1>Second Preference:</h1><p />
                   <apex:selectList id="second" value="{!semName2}" multiselect="false" size="1">
                   <apex:selectOptions value="{!items}"/>
                   </apex:selectList>
             <p />
                    <h1>Third Preference:</h1><p />
                   <apex:selectList id="third" value="{!semName3}" multiselect="false" size="1">
                   <apex:selectOptions value="{!items}"/>
                   </apex:selectList>
</apex:PageBlock>
      </apex:form>

     <!-- Java script starts Here -->
  <script>
   function validateFunction(first){
       var inputAmount = document.getElementById(first).value;
         if(inputAmount == 'Please Choose a Seminar'){
            alert('Please enter seminar1');
         } 
  }
  </script> 
 <!-- java script ends here -->  

</apex:page>

Answer 1

You can not just access the selected value using .value notation of the object. You have to access the options first and then get the selected option like this:

var inputAmount = document.getElementById(first).value;
var val = inputAmount.options[inputAmount.selectedIndex].value;