Hello guys,
If you want to check and unchecked the checkbox in javascript and jquery use the below code.
For example :

Checkbox: <input type="checkbox" id="checkboxid" class ='checkboxclass'>

Checked and unchecked to checkbox in javascript :

 document.getElementById("checkboxid").checked = true;

  document.getElementById("myCheck").checked = false;

Checked and unchecked to checkbox in JQuery :
jQuery 1.6+
Best way for checked and unchecked by "prop" function in this version.

$('.checkboxclass').prop('checked', true);
$('.checkboxclass').prop('checked', false);

jQuery 1.5.x and below
Best way for checked and unchecked by "attr" function in this version.

$('.checkboxclass').attr('checked', true);
$('.checkboxclass').attr('checked', false);

Remove checked from checkbox :

$('.checkboxclass').removeAttr('checked');