execute a change event on input that was modified by another function

I have a function that does a calculation on an input, I have a function in another script I want to run when the value of the input changes.

I try to do with the change event but does not register the change unless you change the value myself.

$(document).ready(
function(){
    $("#hello").val(1+1);
    $("#hello").change( function(){
        alert("change");
        }
    );
});

the solution I found was

$(document).ready(
function(){
    $("#hello").val(1+1).trigger('change');
    $("#hello").change( function(){
        alert("change");
        }
    );} );

I think you should be attaching the event first & then make the change. Don't you?

Besides you might have to fire the event manually (using .trigger), like this:

$(document).ready(function(){

   $(".hello").change( function(){ alert("change"); });

   $(".hello").val(1+1).trigger("change");

});