Query string value extraction

urlExtractor.js

function urlExtractor(url) {
  url = decodeURIComponent(url);
  
  var charIndex = url.indexOf('=');
  if(charIndex < 0) {
    return;
  }

  var sliced = url.slice(charIndex).substring(1).replace(/_/g, ' ');
  var inputField = document.getElementById('lead_source');
  inputField.value = sliced;
  return;
}
urlExtractor(window.location.href);