Do something if the checkbox is checked

Demo

CheckBox1

Do something if two checkboxes are checked

CheckBox2 CheckBox3 CheckBox4

---

HTML

<!-- If one checkbox is checked -->
<input type="checkbox" id="check1"/>CheckBox1

<!-- If two checkboxes are checked -->
<input type="checkbox" id="check2"/>CheckBox2
<input type="checkbox" id="check3"/>CheckBox3
<input type="checkbox" id="check4"/>CheckBox4

Script

<script>
/* If one checkbox is checked */
$('#check1').click(function () {
    if (jQuery(this).is(':checked')) {
        alert("checked");
            } else {
        alert("unchecked");
    }
});

/* If two checkboxes are checked */
$("input[type=checkbox]").change(function(){
if($('#check2').is(':checked') && $('#check3').is(':checked')) {
   alert("You checked 2 and 3");
}
else if($('#check2').is(':checked') && $('#check4').is(':checked')) {
   alert("You checked 2 and 4");
}
else if($('#check3').is(':checked') && $('#check4').is(':checked')) {
   alert("You checked 3 and 4");
}
});
</script>