Merge branch 'master' into integrate-crowdin

Author: Brian Vaughn

content/blog/2015-12-16-ismounted-antipattern.md

@@ -43,7 +43,7 @@ If you use ES6 promises, you may need to wrap your promise in order to make it c
 
 ```js
 const cancelablePromise = makeCancelable(
-  new Promise(r => component.setState({...}}))
+  new Promise(r => component.setState({...}))
 );
 
 cancelablePromise

content/community/conferences.md

@@ -71,6 +71,11 @@ October 5 in Verona, Italy
 
 [Website](http://2018.reactjsday.it) - [Twitter](https://twitter.com/reactjsday)
 
+### React Day Berlin 2018
+November 30, Berlin, Germany
+
+[Website](https://reactday.berlin) - [Twitter](https://twitter.com/reactdayberlin) - [Facebook](https://www.facebook.com/reactdayberlin/) - [Videos](https://www.youtube.com/channel/UC1EYHmQYBUJjkmL6OtK4rlw)
+
 ## Past Conferences
 
 ### React.js Conf 2015
@@ -220,7 +225,7 @@ November 4 in Seoul, South Korea
 
 [Website](http://seoul.reactjs.kr/en)
 
-### React Day Berlin
+### React Day Berlin 2017
 December 2, Berlin, Germany
 
 [Website](https://reactday.berlin) - [Twitter](https://twitter.com/reactdayberlin) - [Facebook](https://www.facebook.com/reactdayberlin/) - [Videos](https://www.youtube.com/watch?v=UnNLJvHKfSY&list=PL-3BrJ5CiIx5GoXci54-VsrO6GwLhSHEK)

content/docs/reference-glossary.md

@@ -150,7 +150,7 @@ Don't pass something like `Math.random()` to keys. It is important that keys hav
 
 ## [Refs](/docs/refs-and-the-dom.html)
 
-React supports a special attribute that you can attach to any component. The `ref` attribute can be a string or a callback function. When the `ref` attribute is a callback function, the function receives the underlying DOM element or class instance (depending on the type of element) as its argument. This allows you to have direct access to the DOM element or component instance.
+React supports a special attribute that you can attach to any component. The `ref` attribute can be an object created by [`React.createRef()` function](/docs/react-api.html#reactcreateref) or a callback function, or a string (in legacy API). When the `ref` attribute is a callback function, the function receives the underlying DOM element or class instance (depending on the type of element) as its argument. This allows you to have direct access to the DOM element or component instance.
 
 Use refs sparingly. If you find yourself often using refs to "make things happen" in your app, consider getting more familiar with [top-down data flow](/docs/lifting-state-up.html).