How to get data from Json into a placeholder in a textbox

Question

this is the Json and I'm trying to have this transfer so instead of a placeholder in text field it will show the data

var username = '0';
$.ajax({
  type: "POST",
  url: "../../socialnetwork1/resources/backend/user/viewUser",
  data: {username: username},
  success: function(data){viewUser(data)},
});
function viewUser(d){
  var data = JSON.parse(d).data;
  var data = JSON.parse(data);
  console.log(data);
  $('#fName').append(data.fName);
   $('#lName').append(data.lName);
   $('#username').append(data.username);
   $('#email').append(data.email);
   $('#bio').append(data.bio);
   $('#photo').attr("src",data.profilePic);

here is the text field

<p id=""><strong>First Name:&nbsp;&nbsp;<input type="textarea" id="fName" placeholder="John"/></strong></p>

Thank you.