how to add alert in bootstrap 4 code example

Example 1: bootstrap alert box

Alerts in Bootstrap:
--------------------------------
Alert classes you can use to check
.alert-primary
.alert-secondary
.alert-success
.alert-danger
.alert-warning
.alert-info
.alert-light
.alert-dark

Simple alert:
-------------
<div class="alert alert-primary" role="alert">
  This is a primary alert—check it out!
</div>

Alert with close button and decriptive feature:
------------------------------------------------
<div class="alert alert-warning 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>

Trigger via javascript:
$(".alert").alert();

Example 2: change size of alert bootstrap

In Bootstrap (v4 and v5), use this width modifier (w-25, w-50, w-75):

<div class="alert alert-danger w-50" role="alert">
  Here is some text!
</div>