Simple and practical example of all selected anti selected button

 
//All button processing
$(function(){ 
//Click on the selection
$("#checkAll").click(function () {//When you click the all - box
var flag = $("#checkAll").is(":checked");//Determines the state of all selected buttons
var checkItems=document.getElementsByName("checkItem"); 
for(var i=0;i<checkItems.length;i++){ 
checkItems[i].checked = flag; 
} 
}); 
//Click on the item
$("input:checkbox[name='checkItem']").each(function(){ 
$(this).click(function(){ 
if($("input:checkbox[name='checkItem']:checked").length==$("input:checkbox[name='checkItem']").length){ 
document.getElementById("checkAll").checked = true; 
}else{ 
document.getElementById("checkAll").checked = false; 
} 
}); 
}); 
});