You want the :checkbox:checked selector and map to create an array of the values:
var checkedValues = $('input:checkbox:checked').map(function() {
return this.value;
}).get();
If your checkboxes have a shared class it would be faster to use that instead, eg. $('.mycheckboxes:checked'), or for a common name $('input[name="Foo"]:checked')
- Update -
If you don't need IE support then you can now make the map() call more succinct by using an arrow function:
var checkedValues = $('input:checkbox:checked').map((i, el) => el.value).get();