End old tasks in Alfresco from Admin

I have been working with Alfresco for a while now. It is a very comprehensive tool, but today I need delete old tasks in archive task node. 

The purpose of the Workflow JavaScript API is to allow access to Alfresco advanced workflows from within JavaScript. The API supports EMCA Script 1.6 compatible JavaScript. Through this API workflow definitions, instances, paths, tasks and transitions can be accessed and managed.