First, let's simplify the compilePost function. This function should know how to compile a post in a synchronous manner. Let's change the isStaff fetching to a simple argument.

function compilePost(post, isStaff) {

    var source = $('#feed-item-template').html();

    var template = Handlebars.compile(source);

    var context = {

        id: post.id,

        content: post.text,

        author: post.author,

        date: $.timeago(post.date),

        staff: isStaff

    }



    var html= template(context);

    return html;

}

Now, let's create a new method, with a single purpose - checking if a user is member of the staff:

function checkForStaffMemebership() {

    return new Promise(function (resolve, reject) {

        $.ajax({

            url: url,

            success: function (data) {

                var session = $.parseJSON(data);

                if (session.is_staff === 1) {

                    resolve(true);

                } else {

                    resolve(false);

                }

            }

        });

    });

}

This function wraps your original ajax call to the server with a promise, whenever the $.ajax call gets a response from the server, the promise will resolve with the answer whether the user is a staff member or not.

Now, we can write another function to orchestrate the process:

function compilePostAsync(post) {

    return checkForStaffMemebership()

        .then(function (isStaff) {

            return compilePost(post, isStaff);

        });

}

compilePostAsync finds out whether the user is a staff member or not. Then, it's compiling the post.

Please notice that compilePostAsync returns a promise, and thus if you used to have something like:

element.innerHTML = compilePost(post);

Now, you should change it to something like:

compilePostAsync(post).then(function (compiledPost) {

    element.innerHTML = compiledPost;

});

Some notes:

1. This is only an example, it surely misses some things (proper error handling for example)


2. The isStaff and checkForStaffMemebership (original and new) do not get any argument, I guess you'd figure out how to pass the userId or any other data you might need


3. Read about promises, it's a useful tool to have, there is a lot of data about it on the web, for example: MDN.