Functions and synchronous requests

Imagine my JS script is the following :

function big_code() {
        do_a_lot_of_stuff
        $.ajax({
            type: "post",
            url : host + "/function1",
            headers: {"content-type": "application/json"},
            datatype: "json",
            contentType: "application/json; charset=utf-8",
            data: my_variables1 ,
            success:function(){
                      $.ajax({
                      type: "post",
                      url : host + "/function2",
                      headers: {"content-type": "application/json"},
                      datatype: "json",
                      contentType: "application/json; charset=utf-8",
                      data: my_variables2,
                      success:function(data){  VARIABLES = SOMETHING })
    }
  })

 return VARIABLES }


function other_bigfunction() {
        VARIABLES = big_code() 
        do_something_else...

I succeeded to get the variable VARIABLES from big_code function by using async=false in ajax requests.
Of course it is unconvenient because all others functions stop working….

Have you an idea to obtain this variable in big_code() ONLY after ajax requests?

Thank you in advance