find it the value of slecte filed is already selected code example
Example 1: javascript get selected option
var e = document.getElementById("selectElementID");
var value=e.selectElement.options[e.selectedIndex].value;// get selected option value
var text=e.options[e.selectedIndex].text;//get the selected option text
Example 2: get selected value of dropdown in javascript
<body>
<select id="list" style="padding: 10px;" onchange="getSelectValue();">
<option value="js">JavaScript</option>
<option value="php">PHP</option>
<option value="c#">Csharp</option>
<option value="java">Java</option>
<option value="node">Node.js</option>
</select>
<script>
function getSelectValue()
{
var selectedValue = document.getElementById("list").value;
alert(selectedValue);
}
getSelectValue();
</script>
</body>