Answers for "bootsrap inpiut error class in bootstrap 4"

bootstrap 4 input error

<link rel="stylesheet" href="https://maxcdn.bootstrapcdn.com/bootstrap/4.0.0-alpha.6/css/bootstrap.min.css" integrity="sha384-rwoIResjU2yc3z8GV/NPeZWAv56rSmLldC3R/AZzGRnGxQQKnKkoFVhFQhNUwEyJ" crossorigin="anonymous">

<!--
  Title: bootstrap 4 input error
-->
<!--Go to https://www.w3schools.com/bootstrap4/bootstrap_forms.asp for more info-->
<form action="/action_page.php" class="was-validated">
  <div class="form-group">
    <label for="uname">Username:</label>
    <input type="text" class="form-control" id="uname" placeholder="Enter username" name="uname" required>
    <div class="valid-feedback">Valid.</div>
    <div class="invalid-feedback">Please fill out this field.</div>
  </div>
  <div class="form-group">
    <label for="pwd">Password:</label>
    <input type="password" class="form-control" id="pwd" placeholder="Enter password" name="pswd" required>
    <div class="valid-feedback">Valid.</div>
    <div class="invalid-feedback">Please fill out this field.</div>
  </div>
  <div class="form-group form-check">
    <label class="form-check-label">
      <input class="form-check-input" type="checkbox" name="remember" required> I agree on blabla.
      <div class="valid-feedback">Valid.</div>
      <div class="invalid-feedback">Check this checkbox to continue.</div>
    </label>
  </div>
  <button type="submit" class="btn btn-primary">Submit</button>
</form>

bootstrap display error message

<div class="alert alert-success alert-dismissible fade show" role="alert">
  <strong>Holy guacamole!</strong> You should check in on some of those fields below.
  <button type="button" class="close" data-dismiss="alert" aria-label="Close">
    <span aria-hidden="true">&times;</span>
  </button>
</div>