Queue user actions-Ajax Pattern?

I have used gmail countless times and was wondering if there are standard patterns behind this scenario:

1. user wants to attach a big file in the email,clicks attach and the selects the file which has to be attached开发者_运维技巧
2. There is some processing which takes place (uploading to server,virus scans etc) and when this is happening an "uploading attachment" message is displayed
3. Before this action could complete, the user clicks send. The "send" is not processed until the upload is successful. The user actions(upload then send) are queued

Is there a standard implementation pattern for these kind of scenarios where user actions need to be queued without blocking the UI? And more curiously, any jQuery plugin exists for such scenarios ?

Not very sure of the design pattern needed here, but I will start with closely looking at Chain Of Command Design Pattern and delegate pattern.