Измените поле ввода и отправьте текст после щелчка

<!DOCTYPE html>
<html>
<head>
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.5.1/jquery.min.js"></script>
<script>
$(document).ready(function(){
  $("#change").click(function(){
  var $name = $(this);
  if(this.value=="percent"){
     $("#percent_input").show();
    	$("#flat_input").hide();
        this.value = 'flat';
        $name.text('Flat');

    }else{
       $("#percent_input").hide();
    	$("#flat_input").show();
        this.value = 'percent';
        $name.text('Percent');  
    } 
  });
  
});
</script>
</head>
<body>

<button id="change" value="percent">Percent</button>

<input id="percent_input" style="display:none" placeholder="Percent">
<input id="flat_input" style="display:none" placeholder="Flat">

</body>
</html>
Ab R Rakib