jQuery, checkboxes and .is(":checked")

$('#myCheckbox').change(function () {
    if ($(this).prop("checked")) {
        // checked
        return;
    }
    // not checked
});

Note: In older versions of jquery it was OK to use attr. Now it's suggested to use prop to read the state.

There is a work-around that works in jQuery 1.3.2 and 1.4.2:

$("#myCheckbox").change( function() {
    alert($(this).is(":checked"));
});

//Trigger by:
$("#myCheckbox").trigger('click').trigger('change');​​​​​​​​​​​​​

But I agree, this behavior seems buggy compared to the native event.

As of June 2016 (using jquery 2.1.4) none of the other suggested solutions work. Checking attr('checked') always returns undefined and is('checked) always returns false.

Just use the prop method:

$("#checkbox").change(function(e) {

  if ($(this).prop('checked')){
    console.log('checked');
  }
});