onKeys(obj, handler)

Register an event handler on the Map-like object obj to trigger when obj's keyset changes. obj must implement @@can.onKeys to be compatible with can-reflect.onKeys. The function passed as handler will receive an Array of object diffs (see diffObject for the format) as its one argument.

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

obj.set("baz", "quux");  // -> logs '[{"property": "baz", "type": "add", "value": "quux"}]'