<!DOCTYPE html>
<html>
<body>
<p>Click the button to encode a string in base-64.</p>
<button onclick="myFunction()">Try it</button>
<p><strong>Note:</strong> The btoa() method is not supported in IE9 and earlier.</p>
<p id="demo"></p>
<script>
function myFunction() {
var str = "Hello World!";
var enc = window.btoa(str);
var res = "Encoded String: " + enc;
document.getElementById("demo").innerHTML = "The original string: " + str + "<br>" + res;
}
</script>
</body>
</html>