Tryit Editor v2.7

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

<p>This example uses the HTML DOM to assign an "onselect" event to an input element.</p>

Select some text: <input type="text" value="Hello world!" id="myText">

<p id="demo"></p>

<script>
document.getElementById("myText").onselect = function() {myFunction()};

function myFunction() {
    document.getElementById("demo").innerHTML = "You selected some text!";
}
</script>

</body>
</html>