JSFiddle - React, Tailwind, and code Playground

HTML

<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.2.1/jquery.min.js"></script>
<a href="https://www.banggood.com/VIOFO-A119-1440P-160-Degree-Wide-Angle-Car-DVR-With-GPS-Black-p-1068196.html" class="btn_offer_block re_track_btn" target="_blank" rel="nofollow">link</a>

JavaScript

var myRef = jQuery("a.btn_offer_block").attr("href");

if(myRef.indexOf("banggood") != "-1") {
  myRef += "?p=BQ06121739480201506E";
} else if(myRef.indexOf("gearbest") != "-1") {
	myRef += "1234";
}

jQuery("a.btn_offer_block").attr("href",myRef);
alert("New Url: " + myRef);