Question

I have this problem.
I have a function for example called functionA() that needs the results from another function called functionB().

var globalVar="";
function functionA(){
    //...
    functionB();
    //here i have to use the global variable (that is empty because functionB isn't finished)
}
function functionB(){
    //ajax request
    globalVar=ajaxRequest.responseText;
}

How can I do to let the functionB finish befor continue with the execution of functionA?
Thanks!

This is the code:

var ingredientiEsistenti="";
function ShowInserisciCommerciale() {
    getElementiEsistenti();
    JSON.parse(ingredientiEsistenti);
}

function getElementiEsistenti(){

// prendo gli ingredienti esistenti.
var url = "http://127.0.0.1:8080/Tesi/Ingredienti";
var xmlHttp = new XMLHttpRequest();
xmlHttp.open("POST", url, false);
xmlHttp.send(null);
xmlHttp.setRequestHeader("Content-type",
        "application/x-www-form-urlencoded");
xmlHttp.onreadystatechange = function() {
    if (xmlHttp.readyState == 4) // COMPLETED
    {
        if (xmlHttp.status == 200) // SUCCESSFUL
        {
            ingredientiEsistenti = xmlHttp.responseText;
        } else {

            alert("An error occurred while communicating with login server.");
        }
    }
};
}

Answer 1

You’ve got one of many options, that don’t require an evil global variable:

• Move the code you want to see executed to the onreadystatechange callback of the ajax request, that way, it won’t get executed until you received a response

• Redefine functionA, so that it takes a parameter that allows you to skip the first bit:

• Make the request synchronous, not recommended, though

• use a timeout/interval to check the readystate of the request manually (brute-force, not recommended either)

• Perhaps there is some worker trickery that could do the trick, too, in your particular case

---

function functionA(skipDown)
{
    skipDown = skipDown || false;
    if (skipDown === false)
    {
        //doStuff
        return functionB();//<-- call functionA(true); from the readystatechange callback
    }
    //this code will only be called if skipDown was passed
}