Tryit Editor v2.9

Edit This Code:
<!DOCTYPE html>
<html>
<body>

<p id="p1">Select a value from the list below, to change this element's opacity!</p>

<select onchange="myFunction(this);" size="5">
  <option>0
  <option>0.2
  <option>0.5
  <option>0.8
  <option selected="selected">1
</select>

<script>
function myFunction(x) {
// Return the text of the selected option
    var opacity = x.options[x.selectedIndex].text;
    var el = document.getElementById("p1");
    if (el.style.opacity !== undefined) {
        el.style.opacity = opacity;
    } else {
        alert("Your browser doesn't support this example!");
    }
}
</script>

</body>
</html>