I am trying to write a validation block inside my JS to check if the user has selected a value or not and pop up a message if the value is not selected.

function validate(form) {
    var success = true;
    var message = "";

    if (form.dropdown.selectedIndex ==  0 )  {  
        form.save.disabled=true;

        if (0 < message.length) {
            message += "\n"; 
        }
        message += "dropdown  value should be selected.";
    }

    if (0 < message.length) {
        alert(message);
        success = false;
    }

    return success;
}

When I click on Save button I call this function. I don't see errors in the logs. Can anyone tell me what am I doing wrongly here? Or can you guide me what is the correct method to validate if the user has selected a value before allowing to save?

Thanks!

I am trying to write a validation block inside my JS to check if the user has selected a value or not and pop up a message if the value is not selected.

function validate(form) {
    var success = true;
    var message = "";

    if (form.dropdown.selectedIndex ==  0 )  {  
        form.save.disabled=true;

        if (0 < message.length) {
            message += "\n"; 
        }
        message += "dropdown  value should be selected.";
    }

    if (0 < message.length) {
        alert(message);
        success = false;
    }

    return success;
}

When I click on Save button I call this function. I don't see errors in the logs. Can anyone tell me what am I doing wrongly here? Or can you guide me what is the correct method to validate if the user has selected a value before allowing to save?

Thanks!

• javascript
• drop-down-menu

Share Improve this question Follow edited Sep 20, 2012 at 22:52 RobG 148k3232 gold badges179179 silver badges214214 bronze badges asked Sep 20, 2012 at 22:42 smileysmiley 49144 gold badges1515 silver badges3737 bronze badges 3

• @smiley—don't use tabs for indenting, it messes with SO's formatting. – RobG Commented Sep 20, 2012 at 22:53
• Can you use jQuery? It would make this easier. – Tool Commented Sep 20, 2012 at 22:53
• Your code works for me: jsfiddle/jd5Ka. It must be somewhere else in your code. – Ethan Brown Commented Sep 20, 2012 at 22:54

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1 Answer 1

Sorted by: Reset to default 3

If no option is selected, the select element's selectedIndex will be -1. It's remended that one option is always set to selected, that way you know what the default selected option is (user agents may make the first option selected by default if you don't).

So the test:

if (form.dropdown.selectedIndex ==  0 )  {  

will only be true if the first option has the selected attribute. So either test against -1 or make the first option selected by default, e.g.

<select name="dropdown" ...>
  <option selected value="default">Please select an option
  ...
</select>