Get the value of checked checkbox?

I am using this in my code.Try this

var x=$("#checkbox").is(":checked");

If the checkbox is checked x will be true otherwise it will be false.

None of the above worked for me but simply use this:

document.querySelector('.messageCheckbox').checked;

For modern browsers:

var checkedValue = document.querySelector('.messageCheckbox:checked').value;

By using jQuery:

var checkedValue = $('.messageCheckbox:checked').val();

Pure javascript without jQuery:

var checkedValue = null; 
var inputElements = document.getElementsByClassName('messageCheckbox');
for(var i=0; inputElements[i]; ++i){
      if(inputElements[i].checked){
           checkedValue = inputElements[i].value;
           break;
      }
}