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<!DOCTYPE html>
<html>
<head>
    <meta charset="utf-8" />
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <title>Page Title</title>
    <meta name="viewport" content="width=device-width, initial-scale=1">

    <link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.3/css/bootstrap.min.css">

<!-- jQuery library -->
<script src="https://ajax.googleapis.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>

<!-- Popper JS -->
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.3/umd/popper.min.js"></script>

<!-- Latest compiled JavaScript -->
<script src="https://maxcdn.bootstrapcdn.com/bootstrap/4.1.3/js/bootstrap.min.js"></script>
<script>
  $(document).ready(function (){
    $("button").click(function (){
      $.get("https://jsonplaceholder.typicode.com/posts/3", function (data, status) {
    $("#number").val(data.id);
    $("#title").val(data.title);
    $("#body").val(data.body);
      });
    });
  });


</script>
</head>
<nav class="navbar navbar-expand-md bg-dark navbar-dark">
        <!-- Brand -->
        <a class="navbar-brand" href="#">Navbar</a>

        <!-- Toggler/collapsibe Button -->
        <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#collapsibleNavbar">
          <span class="navbar-toggler-icon"></span>
        </button>

        <!-- Navbar links -->
        <div class="collapse navbar-collapse" id="collapsibleNavbar">
          <ul class="navbar-nav">
            <li class="nav-item">
              <a class="nav-link" href="#">Tanja</a>
            </li>
            <li class="nav-item">
              <a class="nav-link" href="#">Form</a>
            </li>
          </ul>
        </div>
      </nav>

<div class="container">
  <h2>Forma</h2>
  <form>
    <div class="form-group">
      <label for="id">ID:</label>
      <input type="text" class="form-control" id="number" name="id">

    </div>
  </form>
  <button class="btn btn-primary" id="dugme">Submit</button>
</div>
<body>

</body>
</html>