queue.flush()

Flushes tasks currently in the task queue. When complete, calls the onComplete callback.

If a CompletionQueue is currently flushing tasks, it prevents additional calls to flush from running tasks. This makes it so each task function finishes running before others are started as demonstrated below:

queue.enqueue( function() {
   console.log( "task 1 - start" );
   queue.flush();
   console.log( "task 1 - end" );
} );

queue.enqueue( function() {
   console.log( "task 2 - start" );
   console.log( "task 2 - end" );
} );

queue.flush();

// console.logs
//    task 1 - start
//    task 1 - end
//    task 2 - start
//    task 2 - end

If the queue's tasks are currently being flushed, new tasks added will be run without needing to call .flush() again.