Make ajax call dependent on another ajax call - ajax

Question

I would to avoid nesting a bunch of ajax calls inside the 'success' event of one another. I was wondering if someone could guide me in the right direction on how to do something like this? Where one ajax call is dependent on another's return value?
The getLoginAccess() function will be used in many other methods in a similar manner.
If the first one fails i would like to just have it return a 'null' value which i can then take into account before running the second ajax call. Below i demonstrate a psuedo example of what im trying to do.
The method getLoginAccess returns a dictionary of data that is required for the second method createItem to execute. So only if getLoginAccess returns valid data will createItem continue on to call the actual ajax call.
Thank you
function getLoginAccess() {
$.ajax({
url: '.../api/v1/auth/access_token',
method: 'POST',
headers: {
'Content-Type': 'application/x-www-form-urlencoded',
'Accept': 'application/json',
'Connection': 'keep-alive'
},
data: {
grant_type: 'client_credentials',
username: 'johnDoe',
password: '******'
},
success: function (data) {
console.log(JSON.stringify(data));
return data;
},
error: function (data) {
console.log(data);
return null;
}
})
}
function createItem() {
var login = getLoginAccess();
if (login == null) {
return false;
}
$.ajax({
url: '.../api/v1',
method: 'POST',
headers = {
'Accept': 'application/json',
'Content-Type': 'application/x-www-form-urlencoded',
'access': `${login.access_token}`
};
data: {},
success: function (data) {
console.log(JSON.stringify(data));
},
error: function (data) {
console.log(data);
}
})
}
window.onload = function(){
createItem();
};

Answer 1

If you want to refactor the part where the login is verified we could create an intermediate function .. something like this:
Your login function here
function getLoginAccess(){
// Return login data or null
}
Here we can create an intermediate function to deal with the dependencies of the next execution. If the login returns something other than null, the function passed as a parameter will be executed.
function intermediateFunction(functionName,login){
if(login){
window[functionName]();
}
}
Here are the other functions you have created.
function createItem() {
// Do something
}
function listItem() {
// Do something
}
Here instead of calling the createItem() function you call the intermediary
window.onload = function(){
intermediateFunction(getLoginAccess(), "createItem");
};
So basically you would always call the intermediate function that would check the login before calling a particular function. I believe that this is how I would refactor :)