Ordering the function calls

Question

I have to call the functions in an order, but somehow they work independently.

Here are the functions:

function a(){
  Ajax_Call_1();
}

function b(){
  Ajax_Call_2();
}

function c(){
  Ajax_Call_3();
}

$.when( a() ).then( $.when( b() ).then( c() ) );

When I run it, it looks like:

A works

C works

B works

But sometimes:

C works

A works

B works

How can I order them?

Answer 1

You can chain promise-like objects with using then method. Note the difference between then and done/fail, a done callback passed to then can return a new promise-like object for the rest of the control flow. This is why you can do the chaining. See the documentation.

a().then(b).then(c).done(function() { // the last promise has been resolved });

All of your functions should return the promise object for this to work. So your b should look like this.

function b(){
  return Ajax_Call_2();
}

Where Ajax_Call itself should return the ajax call, like return $.ajax(...).

Note that as both b and c returns the promise, you can pass them directly to then.