Use onload event attribute
by WittigMarcus
HTML
<body onload=domainRef()>
<div id="divref">
<script>
function domainRef() {
var ref = document.referrer.toString();
document.getElementById("test").value = ref;
}
</script>
</div>
<input id="test" value="">
<p>
Used in my answer to:
</p><a href="https://stackoverflow.com/questions/55533287/how-to-pass-a-variable-into-a-input-value-on-page-load">how-to-pass-a-variable-into-a-input-value-on-page-load</a>
</body>