Event after all ajax calls are complete

I have a click event that fires off 3 ajax calls:

$("#button").click(function(e) {
    e.preventDefault();

    $.ajax(call1);
    $.ajax(call2);
    $.ajax(call3);

    some_function() //should fire off AFTER all ajax calls are complete
});

Is there a way for me to confirm all ajax calls have been fired BEFORE firing off my some_function() function?

Thanks in advance!