JSFiddle - React, Tailwind, and code Playground

HTML

<form>
    <label>Some Input:</label>
    <input id="someInput" />
</form>

JavaScript

function populateForm() {
  var formVal = '';
  var url = 'http://www.smartreliefrx.com/qualify/new/diabetes/?a=1476&oc=172&c=1205&m=2&s1=#affid&s2=#s2&s3=s1#&s5=someValue';
  //var url = window.location.search.substring(1);
  url = url.split('&');
  for(var i=0; i<url.length; i++) {
    var pair = url[i].split('=');
    if(pair[0] == 's5') {
      formVal = pair[1];  
    }
  }
  document.getElementById('someInput').value = formVal;
}

populateForm();