onKeysRemoved(obj, handler)

Register an event handler on the Map-like object obj to trigger when a key or keys are removed from obj's keyset. obj must implement @@can.onKeysRemoved to be compatible with can-reflect.onKeysAdded. The function passed as handler will receive an Array of Strings as its one argument.

var obj = new CanMap({ foo: "bar" });
canReflect.onKeys(obj, function(diffs) {
    console.log(JSON.stringify(diffs));
});

foo.removeAttr("foo");  // -> logs '["foo"]'