Test Case Boilerplate

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HTML

<body>
    <input type="checkbox" name="checkall" value="1" id="checkall" /><br/>
    <input type="checkbox" name="chk[]" value="1" id="chk-1" class="boxes"> Box 1</br>
    <input type="checkbox" name="chk[]" value="2" id="chk-2" class="boxes"> Box 2</br>
</body>

JavaScript

$("#checkall").click(function(){
    if($(this).is(':checked'))
    {
        $.each($(".boxes"), function(index, obj){
            $(obj).attr("checked", true);
        });
    }else{
        $.each($(".boxes"), function(index, obj){
            $(obj).attr("checked", false);
        });
    }    
});