display the browser name on pageload without button click

Question

below is my code which returns broswer name on button click but I want to display it on page load without button click how can I do this on page load without button click

 <button onclick="myFunction()">Try it</button>
    <p id="demo"></p>
    <script>

        function myFunction() {
            if ((navigator.userAgent.indexOf("Opera") || navigator.userAgent.indexOf('OPR')) != -1) {
                alert('Opera');
            }
            else if (navigator.userAgent.indexOf("Chrome") != -1) {
                alert('Chrome');
            }
            else if (navigator.userAgent.indexOf("Safari") != -1) {
                alert('Safari');
            }
            else if (navigator.userAgent.indexOf("Firefox") != -1) {
                alert('Firefox');
            }
            else if ((navigator.userAgent.indexOf("MSIE") != -1) || (!!document.documentMode == true)) //IF IE > 10
            {
                alert('IE');
            }
            else {
                alert('unknown');
            }
        }
    </script>

Answer 1

Add this to the bottom of your script:

document.addEventListener( "DOMContentLoaded", myFunction, false );