How do I change the "This field is required" validation message Jquery

Question

i'm trying to customize the error messages that pop up when a form field isn't valid, however, all that is showing up is "This field is required", but i included a messages block in my code to write my own messages. Could anyone tell me how to fix this? This is my code:

      rules: {
          fullname: {
              required: true,
          }
      },
      messages: {
          fullname: {
              required: "Please enter your full name",
          },
          
      }, 
  submitHandler: function(form) {
    form.submit();
  }
 }); ```