Answers for "how to get checked checkbox value in 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
}

get the value of checkbox in js

element.checked;

how to take value only from the checked checkbox

$(document).ready(function() {
  $('#select').click(function() {
    $('input[type="checkbox"]:checked').each(function() {      // $(':checkbox:checked')
      document.body.append(this.value + ' ');                  // $(this).val()
    });
  });
});

html checkbox status

app.innerHTML = '<h1>Hello, world!</h1>';