Select All the Checkboxs in javascript /자바스크립트로 모두선택 모두해제 하는 함수

<script>
function checkall(A,B,C){
var X=eval("document.forms."+A+"."+B)
for (c=0;c<X.length;c++)
X[c].checked=C
}
</script>

<form name="album">
<input type="checkbox" name="v1">Trey Songz<br>
<input type="checkbox" name="v1">Adele<br>
<input type="checkbox" name="v1">Sam Smith<br>
<input type="checkbox" name="v1">Ed Sheeran<br>
<input type="checkbox" name="v1">Coldplay<br>
</form>
<a href="javascript:checkall('album','v1',true)">Select All</a>
<a href="javascript:checkall('album','v1',false)">Unselect All</a>


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Trey Songz
Adele
Sam Smith
Ed Sheeran
Coldplay