Answers for "get array of checked checkboxes javascript"

javacript is checkbox checked

//using plane javascript 
if(document.getElementById('on_or_off_checkbox').checked) {
    //I am checked
} 

//using jQuery
if($('#on_or_off_checkbox').is(':checked')){
    //I am checked
}

checked all items items in checkbox javascript

$( '#container .toggle-button' ).click( function () {
    $( '#container input[type="checkbox"]' ).prop('checked', this.checked)
  })