Checkbox validation using jQuery

Suppose you have a check box with ID agree_checkbox. You can check whether the checkbox is checked using this jQuery code:
$('#agree_checkbox').prop('checked')

Here is a complete example:

Here is the code that does the check:

$("#myform").on("submit",function(form)
{
    if(!$("#agree_checkbox").prop("checked"))
    {
        $("#agree_chk_error").show();
    }
    else
    {
        $("#agree_chk_error").hide();
    }
    return false;
})