How to unicode or numeric value of given string using Javascript?

Html page:

<button onclick="myFunction()">Try it</button>

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

JavaScript Page:

<script>

function myFunction()

{

    var str = "HELLO WORLD";

    var n = str.charCodeAt(0);

    document.getElementById("demo").innerHTML = n;

}

</script>

Output:

72