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var emailField = document.getElementById("some_id");
emailField.addEventListener('keyup', function (event) {
    isValidEmail = emailField.checkValidity();
  }
);

// regex

var patt = /[\S]+@[a-zA-Z0-9.]+?\.[a-zA-Z]{1,12}/;
if(!patt.test(url_params["email"]))
{
  //bad format
}

  /*  EventListeners */
  nameField.addEventListener("keyup", function(event) {
    // fix: no auto in/valid css / force on input empty
    if(nameField.value == "")
      nameField.setCustomValidity("false")
    else
      nameField.setCustomValidity("");
  });

    // validate
    el = document.getElementById("errorNoticeBox");
    el.innerHTML = "";
    if(url_params["name"].length == 0)
    {
      el.innerHTML += "Name field must not be empty!<br>"
      nameField.setCustomValidity("false");
      return false;
    }else{
      nameField.setCustomValidity("");
    }
    
    if(url_params["email"].length == 0)
    {
      el.innerHTML += "Email field must not be empty!<br>"
      return false;
    }