Selecting and deselecting multiple checkboxes

Add following javascript code

function toogleAllCheckboxValue(val) {
 $('.isSelect').prop('checked', val);
}

function setCheckboxHeaderValue(val) {
 //alert(val);
 if(!val) {
  $('.checkBoxHeader').prop('checked', val);
 } else {
  var flag = true;
  $('.isSelect').each(function() {                     
    if(!$(this).is(':checked')) {
     $('.checkBoxHeader').prop('checked', false);
     flag = false;
     return false;
    }
  });  
  if(flag) {
   $('.checkBoxHeader').prop('checked', true);
  }
 }
} 

Below is the screenshot which shows how these 
functions are related to checkboxes