if input has required alert an error if emptyin jquery

You can use the jQuery val() and trim() functions to check if the input field is empty or not. Here's an example:

HTML:

<input type="text" id="myInput" required>
<button id="myButton">Submit</button>
<div id="error"></div>

jQuery:

$(document).ready(function() {
  $('#myButton').click(function() {
    var inputVal = $('#myInput').val().trim();
    
    if (inputVal === '') {
      $('#error').text('Input field cannot be empty!');
      return false;
    } else {
      $('#error').empty();
      return true;
    }
  });
});

In this example, the code checks if the input field is empty when the submit button is clicked. If it's empty, it displays an error message in the #error div. If it's not empty, it clears the error message and allows the form to be submitted