JavaScript: Check all option for CheckBox Control.

To check all the Checkboxes in the CheckBox Control:
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function Allcheck()
{
var ln=document.getElementsByTagName('input');
for(i=1;i {
var input_type=ln[i].type;
if(input_type=="checkbox")
{
var Chck_ID=ln[i].id.indexOf("Check_All");
if(Chck_ID!=-1)
{
ln[i].checked=true;
}
}
}
}