function getParameterByName(name, url) {
  if (!url) {
    url = window.location.href;
  }
  name        = name.replace(/[\[\]]/g, "\\$&");
  let regex   = new RegExp("[?&]" + name + "(=([^&#]*)|&|#|$)"),
      results = regex.exec(url);
  if (!results) {
    return null;
  }
  if (!results[2]) {
    return '';
  }
  return decodeURIComponent(results[2].replace(/\+/g, " "));
}

function setInfusionValue(target) {
  let element = $('input[name="' + target + '"]');

  if (undefined !== element) {
    element.val(getParameterByName(target));
  }
}

/* set your targets */
$(document).ready(function () {
  setInfusionValue('inf_field_FirstName');
  setInfusionValue('inf_field_LastName');
  setInfusionValue('inf_field_Email');
});