JS Toggle Custom Button Opaciry And Show Cookie SRC

<html>
<body onload="my()"">
<center>
<p id="demo"></p>
<script>
var num=0;
function my() {
document.body.style.background="darkblue";
document.body.style.color="magenta";
var x = document.getElementById("e");
x.style.fontSize = "20px";
x.style.color = "darkblue";
x.style.border="100";
x.style.background="lightblue";
document.body.innerHTML=document.body.innerHTML+(document.cookie);
}
</script>
<button id="e" onclick=";
if(num!=1){
e.style.opacity=1.0
num=1
}else{
e.style.opacity=0.5;
num=0}
my();">Show cookies</button>
</center>
</html>