Merge branch 'master' of https://github.com/reactjs/reactjs.org into sync-2304fa1a

Author: reactjs-translation-bot

content/community/conferences.md

@@ -52,11 +52,6 @@ June 21, 2019 Chicago, Illinois USA
 
 [Website](https://reactloop.com) - [Twitter](https://twitter.com/ReactLoop)
 
-### React Week '19 {#RWNY19}
-July 15-21, 2019. New York City, USA
-
-[Website](https://reactweek.nyc) - [Twitter](https://twitter.com/ReactWeek)
-
 ### React Rally 2019
 August 22-23, 2019. Salt Lake City, USA.
 

content/community/meetups.md

@@ -88,6 +88,7 @@ Do you have a local React.js meetup? Add it here! (Please keep the list alphabet
 
 ## Pakistan {#pakistan}
 * [Karachi](https://www.facebook.com/groups/902678696597634/)
+* [Lahore](https://www.facebook.com/groups/ReactjsLahore/)
 
 ## Peru {#peru}
 * [Lima](https://www.meetup.com/ReactJS-Peru/)
@@ -130,8 +131,8 @@ Do you have a local React.js meetup? Add it here! (Please keep the list alphabet
 * [New York, NY - ReactJS](https://www.meetup.com/NYC-Javascript-React-Group/)
 * [New York, NY - React Ladies](https://www.meetup.com/React-Ladies/)
 * [New York, NY - React Native](https://www.meetup.com/React-Native-NYC/)
-* [New York, NY - ReactNYC](https://www.meetup.com/ReactNYC/)
 * [Palo Alto, CA - React Native](https://www.meetup.com/React-Native-Silicon-Valley/)
+* [Philadelphia, PA - ReactJS](https://www.meetup.com/RQ-React/)
 * [Phoenix, AZ - ReactJS](https://www.meetup.com/ReactJS-Phoenix/)
 * [Pittsburgh, PA - ReactJS/React Native](https://www.meetup.com/ReactPgh/)
 * [Portland, OR - ReactJS](https://www.meetup.com/Portland-ReactJS/)

content/docs/optimizing-performance.md

@@ -430,6 +430,6 @@ x === z; // true
 
 In this case, since a new reference is returned when mutating `x`, we can use a reference equality check `(x === y)` to verify that the new value stored in `y` is different than the original value stored in `x`.
 
-Two other libraries that can help use immutable data are [seamless-immutable](https://github.com/rtfeldman/seamless-immutable) and [immutability-helper](https://github.com/kolodny/immutability-helper).
+Other libraries that can help use immutable data include [Immer](https://github.com/mweststrate/immer), [immutability-helper](https://github.com/kolodny/immutability-helper), and [seamless-immutable](https://github.com/rtfeldman/seamless-immutable).
 
 Immutable data structures provide you with a cheap way to track changes on objects, which is all we need to implement `shouldComponentUpdate`. This can often provide you with a nice performance boost.

content/docs/reference-glossary.md

@@ -122,7 +122,7 @@ class Welcome extends React.Component {
 
 A component needs `state` when some data associated with it changes over time. For example, a `Checkbox` component might need `isChecked` in its state, and a `NewsFeed` component might want to keep track of `fetchedPosts` in its state.
 
-The most important difference between `state` and `props` is that `props` are passed from a parent component, but `state` is managed by the component itself. A component cannot change its `props`, but it can change its `state`. To do so, it must call `this.setState()`. Only components defined as classes can have state.
+The most important difference between `state` and `props` is that `props` are passed from a parent component, but `state` is managed by the component itself. A component cannot change its `props`, but it can change its `state`.
 
 For each particular piece of changing data, there should be just one component that "owns" it in its state. Don't try to synchronize states of two different components. Instead, [lift it up](/docs/lifting-state-up.html) to their closest shared ancestor, and pass it down as props to both of them.