single-add-remove.ejs

// remove the association with task1
project.setTasks([task2]).on('success', function(associatedTasks) {
  // you will get task2 only
})

// remove 'em all
projects.setTasks([]).on('success', function(associatedTasks) {
  // you will get an empty array
})

// or remove 'em more directly
projects.removeTask(task1).on('success', function() {
  // it's gone
})

// and add 'em again
projects.addTask(task1).on('success', function() {
  // it's back again
})