Traversing a tree asynchronously with Promise

traverse

traversePromise(callback: ((n: Node) => Promise<void>)): Array<Promise<void>> {
    let queue: Array<Promise<void>> = [];

    let recursion = (node: Node) => {
        if (node.children) {
            node.children.forEach(function (child: Node) {
                queue.push(callback.apply(this, [child]));
                recursion(child)
            });
        }
    }
    recursion(this);
    return queue;
}

This code sample is used to perform async operations on a tree structure. For instance, call a REST API to retrieve profile picture for each one of the employee profile in a organization chart.