check checkbox is checked or not in background jquery code example

Example 1: jquery set checkbox checked

//jQuery 1.6+ use
$('.checkbox').prop('checked', true);
//jQuery 1.5.x and below use
$('.checkbox').attr('checked', true);

Example 2: set checkbox checked jquery

$("#checkboxid").prop('checked', true);  // Checks the box
$("#checkboxid").prop('checked', false); // Unchecks the box