bulk_delete.js

var docs = [ 
  { _id: 'foo',
    _rev: '1-70aa8fe77bbe596bded4a9de3aa185e4',
    "foo": "bar"
  },
  { _id: 'bar',
    _rev: '1-70aa8fe77bbe596bded4a9de3aa185e4',
    "bar": "foo"
  }
]

docs = docs.map(function(doc){
  var del = {};
  del['_id'] = doc['_id'];
  del['_rev'] = doc['_rev'];
  del['_deleted'] = true;
  return del;
});

db.save(docs, callback);