Check/Uncheck all

HTML

<input type="checkbox" class="myChecks" value="1" />
<input type="checkbox" class="myChecks" value="2" />
<input type="checkbox" class="myChecks" value="3" />
<input type="checkbox" class="myChecks" value="4" />
<br/>
<input type="checkbox" id="checkAll" value="" />Check all
<input type="button" id="UncheckAll" value="Uncheck all" />
<input type="button" id="CheckUncheckAll" value="Check/Uncheck all" />

JavaScript

$("#checkAll").click(function() {
alert("kk");
    $(".myChecks").attr('checked', true);
});
    
$("#UncheckAll").click(function() {
    $(".myChecks").attr('checked', false);
});

var isAllChecked = false;

$("#CheckUncheckAll").click(function() {
   isAllChecked = !isAllChecked;  
   $('.myChecks').prop('checked', !isAllChecked  );
});