I am using the following javascript code to check for nothing being entered in a form and it is not working. Can anyone suggest a reason?

           function validateForm()
{
    var a=document.getElementById("quiz_01").value;
    $question = a;
    if (a=="" || a==null) {
      alert("Question 201 must be filled out");
      form1.quiz_01.focus();
      return false;
      }
}

An extract of the html is as follows:

<form id="form1" name="form1" method="post" action=""  onsubmit="return validateForm()">
<table class="table">
    <tr>
        <td>
            <label for="quiz_01">201 A one followed by 100 zeros is a Googol</label>
        </td>
        <td>
            <select name="quiz_01" id="quiz_01">
                <option value=" "> </option>
                <option value="100">100</option>
                <option value="90">90</option>
                <option value="80">80</option>
                <option value="70">70</option>
                <option value="60">60</option>
                <option value="50">50</option>
                <option value="40">40</option>
                <option value="30">30</option>
                <option value="20">20</option>
                <option value="10">10</option>
                <option value="0">0</option>
            </select>
        </td>
    </tr>
</table>
<p>
    <input type="submit" name="next" value="Next &gt;">
</p>

I am using the following javascript code to check for nothing being entered in a form and it is not working. Can anyone suggest a reason?

           function validateForm()
{
    var a=document.getElementById("quiz_01").value;
    $question = a;
    if (a=="" || a==null) {
      alert("Question 201 must be filled out");
      form1.quiz_01.focus();
      return false;
      }
}

An extract of the html is as follows:

<form id="form1" name="form1" method="post" action=""  onsubmit="return validateForm()">
<table class="table">
    <tr>
        <td>
            <label for="quiz_01">201 A one followed by 100 zeros is a Googol</label>
        </td>
        <td>
            <select name="quiz_01" id="quiz_01">
                <option value=" "> </option>
                <option value="100">100</option>
                <option value="90">90</option>
                <option value="80">80</option>
                <option value="70">70</option>
                <option value="60">60</option>
                <option value="50">50</option>
                <option value="40">40</option>
                <option value="30">30</option>
                <option value="20">20</option>
                <option value="10">10</option>
                <option value="0">0</option>
            </select>
        </td>
    </tr>
</table>
<p>
    <input type="submit" name="next" value="Next &gt;">
</p>

• javascript
• html
• forms

Share Improve this question Follow asked Jul 1, 2013 at 11:13 GeoffGeoff 19722 silver badges1313 bronze badges

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6 Answers 6

Sorted by: Reset to default 2

The first option:

<option value=" "> </option>

Has a value that is a single space, not an empty string. So either change the value or change the JS code. Note also that the .value property will never be null so you don't need to test for that.

if (a == " ") {

Demo: http://jsfiddle/RyN5W/

Trim the whitespaces.

 var a=document.getElementById("quiz_01").value.trim();

change

if (a=="" || a==null)

to

if (a==" " || a==null)

You should be checking for " " as per your HTML

if (a == " ") {

change the code to

var e = document.getElementById("quiz_01");
    var ev = e.options[e.selectedIndex].text;

if(ev===' '){
alert('question 201 is a required field');

}

you should use === not == whwn paring strings

You could not access the value directly when working with an <select> element. use following:

var element = document.getElementById("quiz_01");
var a = element.options[element.selecedIndex];

EDIT: (credits to nnnnnn)
In modern browsers the direct access will work, but if you're targeting an old Version (I think especially of Internet Explorer ;) ) the showed approach will gain you patibility.