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Javascript function to validate html select or drop down list

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Introduction:

In my previous article I have explained about Code used to How to show confirmation message while deleting grid view row. In this article I am going to explain about how validate drop down list or html select using Javascript.

Explanation:
For the explanation purpose I have a select list which contains city list along with select city as items. While clicking on the button it will check the selected index of the select. If it is 0 then it will show the alert as city is not selected. Else it will show the message as city is selected.

Below is the code used.
<div>
    <select id="selCity">
        <option>Select City</option>
        <option>Chennai</option>
        <option>Mumbai</option>
        <option>Kolkatta</option>
        <option>Delhi</option>
    </select>
    <br/>
    <input type="button" value="Test" onclick="return fnValidateDropDown();"  />
</div>
<script type="text/javascript">
    function fnValidateDropDown() {
        var obj = document.getElementById('selCity');
        if (obj) {
            if (obj.selectedIndex > 0 && obj.options[obj.selectedIndex].value != "-1") {
                alert('City value is selected');
                return true;
            }
            else {
                alert('City value is not selected');
                return false;
            }
        }
        else
            return false;
    }
</script>

Check the demo here.
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