basic-tab-cloak.html

<link rel="icon">

<input id="title" placeholder="Enter a title">
<button onclick="setTitle()">Set</button>

<input id="icon" placeholder="Enter a favicon URL">
<button onclick="setIcon()">Set</button>

<script>
function setTitle() {
var title = document.getElementById("title")

if (title.value) {
document.title = title.value
}
}

function setIcon() {
var icon = document.getElementById("icon")

if (icon.value) {
document.querySelector("link[rel='icon']").href = icon.value
}
}
</script>