Merge pull request #2795 from romanstetsyk/part1d-links

part1d. Update links to react docs

Author: mluukkai

src/content/1/en/part1d.md

@@ -160,7 +160,7 @@ The application appears to work. However, <i>it is forbidden in React to mutate
 
 Storing all of the state in a single state object is a bad choice for this particular application; there's no apparent benefit and the resulting application is a lot more complex. In this case, storing the click counters into separate pieces of state is a far more suitable choice.
 
-There are situations where it can be beneficial to store a piece of application state in a more complex data structure. [The official React documentation](https://reactjs.org/docs/hooks-faq.html#should-i-use-one-or-many-state-variables) contains some helpful guidance on the topic.
+There are situations where it can be beneficial to store a piece of application state in a more complex data structure. [The official React documentation](https://react.dev/learn/choosing-the-state-structure) contains some helpful guidance on the topic.
 
 ### Handling arrays
 
@@ -317,7 +317,7 @@ Even though a new value was set for _left_ by calling _setLeft(left + 1)_, the o
 setTotal(left + right) 
 ```
 
-The reason for this is that a state update in React happens [asynchronously](https://reactjs.org/docs/state-and-lifecycle.html#state-updates-may-be-asynchronous), i.e. not immediately but "at some point" before the component is rendered again.
+The reason for this is that a state update in React happens [asynchronously](https://react.dev/learn/queueing-a-series-of-state-updates), i.e. not immediately but "at some point" before the component is rendered again.
 
 We can fix the app as follows:
 
@@ -391,7 +391,7 @@ And in all other cases, the component renders the clicking history:
 
 The <i>History</i> component renders completely different React elements depending on the state of the application. This is called <i>conditional rendering</i>.
 
-React also offers many other ways of doing [conditional rendering](https://reactjs.org/docs/conditional-rendering.html). We will take a closer look at this in [part 2](/en/part2).
+React also offers many other ways of doing [conditional rendering](https://react.dev/learn/conditional-rendering). We will take a closer look at this in [part 2](/en/part2).
 
 Let's make one last modification to our application by refactoring it to use the _Button_ component that we defined earlier on:
 
@@ -451,7 +451,7 @@ const App = () => {
 
 ### Old React
 
-In this course, we use the [state hook](https://reactjs.org/docs/hooks-state.html) to add state to our React components, which is part of the newer versions of React and is available from version [16.8.0](https://www.npmjs.com/package/react/v/16.8.0) onwards. Before the addition of hooks, there was no way to add state to functional components. Components that required state had to be defined as [class](https://reactjs.org/docs/react-component.html) components, using the JavaScript class syntax.
+In this course, we use the [state hook](https://react.dev/learn/state-a-components-memory) to add state to our React components, which is part of the newer versions of React and is available from version [16.8.0](https://www.npmjs.com/package/react/v/16.8.0) onwards. Before the addition of hooks, there was no way to add state to functional components. Components that required state had to be defined as [class](https://react.dev/reference/react/Component) components, using the JavaScript class syntax.
 
 In this course, we have made the slightly radical decision to use hooks exclusively from day one, to ensure that we are learning the current and future variations of React. Even though functional components are the future of React, it is still important to learn the class syntax, as there are billions of lines of legacy React code that you might end up maintaining someday. The same applies to documentation and examples of React that you may stumble across on the internet.
 
@@ -1115,7 +1115,7 @@ The internet is full of React-related material. However, we use the new style of
 
 You may find the following links useful:
 
-- The [official React documentation](https://reactjs.org/docs/hello-world.html) is worth checking out at some point, although most of it will become relevant only later on in the course. Also, everything related to class-based components is irrelevant to us;
+- The [official React documentation](https://react.dev/learn) is worth checking out at some point, although most of it will become relevant only later on in the course. Also, everything related to class-based components is irrelevant to us;
 - Some courses on [Egghead.io](https://egghead.io) like [Start learning React](https://egghead.io/courses/start-learning-react) are of high quality, and the recently updated [Beginner's Guide to React](https://egghead.io/courses/the-beginner-s-guide-to-reactjs) is also relatively good; both courses introduce concepts that will also be introduced later on in this course. **NB** The first one uses class components but the latter uses the new functional ones.
 
 ### Web programmers oath