select and unselect all checkbox by javascript

<div class="mt10">

<a href="javascript:;" class="c068 bline" onclick="getCheckedBoxes('check[]',1)">Select all</a>&nbsp;&nbsp;&nbsp;&nbsp;

<a href="javascript:;" class="c068 bline" onclick="getCheckedBoxes('check[]',2)">Select none</a>&nbsp;&nbsp;&nbsp;&nbsp;

<a href="javascript:;" class="c068 bline" onclick="return deletfavorite();">Delete selected</a>

<!-- <form name="searchForm" action="" method="post">
<input id="key" name="search" style="width:200px" value="" class="input1" type="text">
<input type="submit" name="submit" value="Search">
</form> -->
</div>
<form name="list" method="post" action="">
<p>
<input name="check[]" type="checkbox" value="11">c1
</p>
<p>
<input name="check[]" type="checkbox" value="11">c2
</p>
<p>
<input name="check[]" type="checkbox" value="11">c3
</p>
<p>
<input name="check[]" type="checkbox" value="11">c4
</p>
</form>


<script>

 jQuery('#mydesign').attr('class','active');

function getCheckedBoxes(chkboxName,val) {

 var checkboxes = document.getElementsByName(chkboxName);

 var checkboxesChecked = [];

 // loop over them all

   for (var i=0; i<checkboxes.length; i++) {

// And stick the checked ones onto an array...

if(val==1){

checkboxes[i].checked='checked';

}

 if(val==2){

  checkboxes[i].checked='';

 }



 }



}





function deletfavorite(){

var checkboxes = document.getElementsByName('check[]');

$check=false;

for (var i=0; i<checkboxes.length; i++) {

if(checkboxes[i].checked){

$check=true;

break;

}



}



if($check){

var r=confirm("Conform to Delete!")

if (r==true){

document.list.submit();

}else{

return false;

}



}else{

alert('Check At list One Option!');

}



}





</script>