I have a list of users. Each user has a checkbox having a unique value. There is a dropdown menu. And when the dropdown is changed, a set of users are checked. Each dropdown change, a new set of users are checked. This much is working properly. But I'm not able to clear the previous checkboxes checked based on the last selected dropdown value
HTML
    $(document).ready(function() {
      $('#ddl').on('change', function() {
        var selectedShift = this.value;
        //$('input:checkbox').attr('checked',false);
        //$(".shiftUsersClass").attr('checked', false);
        if (selectedShift == 1) {
          var result = [{
            "staff_id": "367"
          }, {
            "staff_id": "864"
          }];
        }
        if (selectedShift == 2) {
          var result =[{"staff_id":"370"}];
        }
        if (selectedShift == 3) {
          var result= [{"staff_id":"369"}];
        }
        if (selectedShift == 4) {
          var result= [{"staff_id":"378"}];
        }
        if (selectedShift == 5) {
          var result=[{"staff_id":"511"}];
        }
    
        $.each(result, function(index, res) {
          $("#shiftUsers" + res.staff_id).attr('checked', 'checked');
        });
    
      });
    });<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<div>
    <div class="form-group">
      <label>Select One</label>
      <select name="ddl" id="ddl" data-placeholder="-- Select --" class="form-control select2">
        <option value="">All</option>
        <option value="1">
          One </option>
        <option value="2">
          Two </option>
        <option value="3">
          Third </option>
        <option value="4">
          Four </option>
        <option value="5">
          Five </option>
      </select>
    </div>
    
    
    <div id="user367" class="col-md-4">
      <div class="box box-danger">
        <div class="box-header with-border">
          <h3 class="box-title">steve</h3>
    
          <div class="box-tools pull-right">
            <div class="checkbox">
              <label>
                <input id="shiftUsers367" class="shiftUsersClass" name="shiftUsers" type="checkbox" value="367">
              </label>
            </div>
          </div>
        </div>
      </div>
    </div>
    <div id="user369" class="col-md-4">
      <div class="box box-danger">
        <div class="box-header with-border">
          <h3 class="box-title">sam</h3>
    
          <div class="box-tools pull-right">
            <div class="checkbox">
              <label>
                <input id="shiftUsers369" class="shiftUsersClass" name="shiftUsers" type="checkbox" value="369">
              </label>
            </div>
          </div>
        </div>
      </div>
    </div>
    <div id="user370" class="col-md-4">
      <div class="box box-danger">
        <div class="box-header with-border">
          <h3 class="box-title">martha</h3>
    
          <div class="box-tools pull-right">
            <div class="checkbox">
              <label>
                <input id="shiftUsers370" class="shiftUsersClass" name="shiftUsers" type="checkbox" value="370">
              </label>
            </div>
          </div>
        </div>
      </div>
    </div>
    <div id="user378" class="col-md-4">
      <div class="box box-danger">
        <div class="box-header with-border">
          <h3 class="box-title">bonnie</h3>
    
          <div class="box-tools pull-right">
            <div class="checkbox">
              <label>
                <input id="shiftUsers378" class="shiftUsersClass" name="shiftUsers" type="checkbox" value="378">
              </label>
            </div>
          </div>
        </div>
      </div>
    </div>
    <div id="user511" class="col-md-4">
      <div class="box box-danger">
        <div class="box-header with-border">
          <h3 class="box-title">cathy</h3>
    
          <div class="box-tools pull-right">
            <div class="checkbox">
              <label>
                <input id="shiftUsers511" class="shiftUsersClass" name="shiftUsers" type="checkbox" value="511">
              </label>
            </div>
          </div>
        </div>
      </div>
    </div>
    <div id="user864" class="col-md-4">
      <div class="box box-danger">
        <div class="box-header with-border">
          <h3 class="box-title">jordan</h3>
    
          <div class="box-tools pull-right">
            <div class="checkbox">
              <label>
                <input id="shiftUsers864" class="shiftUsersClass" name="shiftUsers" type="checkbox" value="864">
              </label>
            </div>
          </div>
        </div>
      </div>
    </div>
    </div>Things I tried 1) Tried to clear all the previously checked checkbox for each change of dropdown value.
$('input:checkbox').attr('checked',false);
2) Added a class for each checkbox and tried to uncheck the previously checked checkbox for each change of dropdown value.
$(".shiftUsersClass").attr('checked', false);
When I tried both the option, no checkboxes are getting checked. What's causing this issue? Thanks!
 
     
     
    