Merge branch 'master' of https://github.com/reactjs/reactjs.org into sync-99a18287

Author: reactjs-translation-bot

content/community/conferences.md

@@ -12,16 +12,6 @@ Do you know of a local React.js conference? Add it here! (Please keep the list c
 
 ## Upcoming Conferences {#upcoming-conferences}
 
-### React Summit 2019 {#reactsummit2019}
-November 30, 2019 in Lagos, Nigeria
-
-[Website](https://reactsummit2019.splashthat.com) -[Twitter](https://twitter.com/react_summit)
-
-### React Day Berlin 2019 {#react-day-berlin-2019}
-December 6, 2019 in Berlin, Germany
-
-[Website](https://reactday.berlin) - [Twitter](https://twitter.com/reactdayberlin) - [Facebook](https://www.facebook.com/reactdayberlin/) - [Videos](https://www.youtube.com/reactdayberlin)
-
 ### React Barcamp Cologne 2020 {#react-barcamp-cologne-2020}
 February 1-2, 2020 in Cologne, Germany
 
@@ -87,6 +77,10 @@ September 1, 2020 in Melbourne, Australia
 
 [Website](https://www.componentsconf.com.au/) - [Twitter](https://twitter.com/ComponentsConf) - [Facebook](https://www.facebook.com/ComponentsConf/) - [LinkedIn](https://www.linkedin.com/company/componentsconf/) - [YouTube](https://www.youtube.com/ComponentsConf)
 
+### React India 2020 {#react-india-2020}
+November 6, 2020 in Mumbai, India
+
+[Website](https://www.reactindia.io) - [Twitter](https://twitter.com/react_india) - [Facebook](https://www.facebook.com/ReactJSIndia/) - [LinkedIn](https://www.linkedin.com/showcase/14545585) - [YouTube](https://www.youtube.com/channel/UCaFbHCBkPvVv1bWs_jwYt3w/videos)
 
 ## Past Conferences {#past-conferences}
 
@@ -481,3 +475,14 @@ October 25, 2019 in London, UK
 October 19, 2019 in São Paulo, BR
 
 [Website](https://reactconf.com.br/) - [Twitter](https://twitter.com/reactconfbr) - [Facebook](https://www.facebook.com/ReactAdvanced) - [Slack](https://react.now.sh/)
+
+### React Summit 2019 {#reactsummit2019}
+November 30, 2019 in Lagos, Nigeria
+
+[Website](https://reactsummit2019.splashthat.com) -[Twitter](https://twitter.com/react_summit)
+
+### React Day Berlin 2019 {#react-day-berlin-2019}
+December 6, 2019 in Berlin, Germany
+
+[Website](https://reactday.berlin) - [Twitter](https://twitter.com/reactdayberlin) - [Facebook](https://www.facebook.com/reactdayberlin/) - [Videos](https://www.youtube.com/reactdayberlin)
+

content/docs/optimizing-performance.md

@@ -176,7 +176,7 @@ To do this in Chrome:
 
 6. React events will be grouped under the **User Timing** label.
 
-For a more detailed walkthrough, check out [this article by Ben Schwarz](https://building.calibreapp.com/debugging-react-performance-with-react-16-and-chrome-devtools-c90698a522ad).
+For a more detailed walkthrough, check out [this article by Ben Schwarz](https://calibreapp.com/blog/react-performance-profiling-optimization).
 
 Note that **the numbers are relative so components will render faster in production**. Still, this should help you realize when unrelated UI gets updated by mistake, and how deep and how often your UI updates occur.
 

content/docs/refs-and-the-dom.md

@@ -140,7 +140,7 @@ class CustomTextInput extends React.Component {
 
 #### Refs and Function Components {#refs-and-function-components}
 
-**You may not use the `ref` attribute on function components** because they don't have instances:
+By default, **you may not use the `ref` attribute on function components** because they don't have instances:
 
 ```javascript{1,8,13}
 function MyFunctionComponent() {
@@ -161,7 +161,7 @@ class Parent extends React.Component {
 }
 ```
 
-You should convert the component to a class if you need a ref to it, just like you do when you need lifecycle methods or state.
+If you want to allow people to take a `ref` to your function component, you can use [`forwardRef`](https://reactjs.org/docs/forwarding-refs.html) (possibly in conjunction with [`useImperativeHandle`](/docs/hooks-reference.html#useimperativehandle)), or you can convert the component to a class.
 
 You can, however, **use the `ref` attribute inside a function component** as long as you refer to a DOM element or a class component:
 

content/docs/testing-environments.md

@@ -53,6 +53,6 @@ Sometimes, you may not want to mock timers. For example, maybe you're testing an
 
 ### End-to-end tests {#end-to-end-tests-aka-e2e-tests}
 
-End-to-end tests are useful for testing longer workflows, especially when they're critical to your business (such as payments or signups). For these tests, you'd probably want to test both how a real browser renders the whole app, fetches data from the real API endpoints, uses sessions and cookies, navigates between different links. You might also likely want to make assertions not just on the DOM state, but on the backing data as well (e.g. to verify whether the updates have been persisted to the database).
+End-to-end tests are useful for testing longer workflows, especially when they're critical to your business (such as payments or signups). For these tests, you'd probably want to test how a real browser renders the whole app, fetches data from the real API endpoints, uses sessions and cookies, navigates between different links. You might also likely want to make assertions not just on the DOM state, but on the backing data as well (e.g. to verify whether the updates have been persisted to the database).
 
 In this scenario, you would use a framework like [Cypress](https://www.cypress.io/) or a library like [puppeteer](https://github.com/GoogleChrome/puppeteer) so you can navigate between multiple routes and assert on side effects not just in the browser, but potentially on the backend as well.

content/docs/testing-recipes.md

@@ -396,14 +396,14 @@ it("changes value when clicked", () => {
 
   // get ahold of the button element, and trigger some clicks on it
   const button = document.querySelector("[data-testid=toggle]");
-  expect(button.innerHTML).toBe("Turn off");
+  expect(button.innerHTML).toBe("Turn on");
 
   act(() => {
     button.dispatchEvent(new MouseEvent("click", { bubbles: true }));
   });
 
   expect(onChange).toHaveBeenCalledTimes(1);
-  expect(button.innerHTML).toBe("Turn on");
+  expect(button.innerHTML).toBe("Turn off");
 
   act(() => {
     for (let i = 0; i < 5; i++) {