jquery checkbox all checked code example

Example 1: How to check whether a checkbox is checked in jQuery?

//using plane javascript 
if(document.getElementById('on_or_off_checkbox').checked) {
    //I am checked
} 

//using jQuery
if($('#on_or_off_checkbox').is(':checked')){
    //I am checked
}

Example 2: jquery get all checkbox checked

$('.theClass:checkbox:checked')

Example 3: select all checkbox jquery

$('#select_all').change(function() {
  var checkboxes = $(this).closest('form').find(':checkbox');
  checkboxes.prop('checked', $(this).is(':checked'));
});

Example 4: select all checkbox jquery

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<form>
  <table>
    <tr>
      <td><input type="checkbox" id="select_all" /></td>
    </tr>
    <tr>
      <td><input type="checkbox" name="select[]" /></td>
    </tr>
    <tr>
      <td><input type="checkbox" name="select[]" /></td>
    </tr>
    <tr>
      <td><input type="checkbox" name="select[]" /></td>
    </tr>
  </table>
</form>