JSFiddle - React, Tailwind, and code Playground
HTML
<form action="">
<p>
<input type="text" id="TEXT_ID" />
<input type="button" value="Go" onclick="GET_IT();" />
</p>
</form>
<iframe id="myFrame" src="http://www.w3schools.com"></iframe>
JavaScript
function GET_IT() {
//var link = document.getElementById("LINKHERE");
//var hrefOrig = link.href;
var hrefOrig = "http://www.google.com"
var dd = document.getElementById("TEXT_ID").value;
var newSrc = hrefOrig + "/" + dd;
alert(newSrc);
document.getElementById('myFrame').src = newSrc;
}