Merge branch 'source' into part6-spanish

Author: pablo-maff

src/content/0/en/part0a.md

@@ -19,7 +19,7 @@ Participants are expected to have good programming skills, basic knowledge of we
 
 Previous knowledge of JavaScript or other course topics is not required.
 
-How much programming experience is needed? It is hard to say, but you should be pretty fluent with *your* language. This level of fluency takes usually at least 100-200 hours of practice to develop.
+How much programming experience is needed? It is hard to say, but you should be pretty fluent in *your* language. This level of fluency takes usually at least 100-200 hours of practice to develop.
 
 ### Course material
 
@@ -37,7 +37,7 @@ The course contains fourteen parts, the first of which is numbered 0 for consist
 
 Proceeding from part *n* to part *n+1* is not sensible before enough know-how of the topics in part *n* has been achieved. In pedagogic terms, the course uses [Mastery Learning](https://en.wikipedia.org/wiki/Mastery_learning), and you are only intended to proceed to the next part after doing enough of the exercises of the previous part.
 
-In parts 1-4 you are expected to do at least **all** of the exercises that are **not** marked with an asterisk(*). Exercises marked with an asterisk count towards your final grade, but skipping them does not prevent you from doing the compulsory exercises in the next parts. Parts 5-13 do not have asterisk marked exercises since there is no similar dependency on previous parts.
+In parts 1-4 you are expected to do at least **all** of the exercises that are **not** marked with an asterisk(*). Exercises marked with an asterisk count towards your final grade, but skipping them does not prevent you from doing the compulsory exercises in the next parts. Parts 5-13 do not have asterisk-marked exercises since there is no similar dependency on previous parts.
 
 The speed of completing the course is flexible.
 
@@ -57,7 +57,7 @@ it is quite likely that nobody will respond. The bug can be *anywhere*.
 
 A better question could be
 
-> * In the exercise 2.15 when I try to add a new person to the app, server responds to 403, despite the request looks ok to me.
+> * In exercise 2.15 when I try to add a new person to the app, the server responds to 403, despite the request looking ok to me.
 >
 > The code looks like this
 >
@@ -74,7 +74,7 @@ A better question could be
 >
 > The network tab looks like the following*
 >
-> [screen shot from the network console]
+> [screenshot from the network console]
 >
 > All the code can be found here (a link to GitHub)
 
@@ -194,7 +194,7 @@ How to study the course – instructions in a nutshell: other course parts
 
 ### Submitting exercises
 
-The exercises are submitted through GitHub and marking them as done on the "my submissions" tab of the [submission application](https://studies.cs.helsinki.fi/stats/courses/fullstackopen).
+The exercises are submitted through GitHub and marked as done on the "my submissions" tab of the [submission application](https://studies.cs.helsinki.fi/stats/courses/fullstackopen).
 
 If you are submitting exercises from different parts to the same repository, use an appropriate system for naming your directories. You can of course create a new repository for each part. If you are using a private repository, add *mluukkai* as a collaborator.
 
@@ -274,11 +274,11 @@ When pressed twice you should see the following text
 
 **Please note** that to get university credits you need a registration for each completed part. Please see [more information about registration](/en/part0/general_info#parts-and-completion).
 
-You can view your grade in University of Helsinki Sisu and [Opintopolku](https://opintopolku.fi/oma-opintopolku/) approximately four weeks after notifying us.
+You can view your grade in the University of Helsinki Sisu and [Opintopolku](https://opintopolku.fi/oma-opintopolku/) approximately four weeks after notifying us.
 
 When the registration is done, the following text appears in the submission system
 
-> *University credits registered, see the course page how to get a transcript if you need one*
+> *University credits registered, see the course page for how to get a transcript if you need one*
 
 ### Where do I get my University of Helsinki Student number
 
@@ -302,11 +302,11 @@ After course enrollment, you will receive a confirmation email to an email addre
 
 #### C) Contact Student Services
 
-If you have trouble finding your student number through the means listed above, you can send an email to University of Helsinki Student Services. ***Make sure you have enrolled in the course through the Open University before sending the email!***
+If you have trouble finding your student number through the means listed above, you can send an email to the University of Helsinki Student Services. ***Make sure you have enrolled in the course through the Open University before sending the email!***
 
 In your email, include the following information
 
-- name of the course you have enrolled in,
+- the name of the course you have enrolled in,
 - your name
 - your date of birth.
 

src/content/10/en/part10c.md

@@ -471,7 +471,7 @@ Note that it is <i>never</i> a good idea to put sensitive data into the applicat
 
 Instead of the hardcoded Apollo Server's URL, use an environment variable defined in the <i>.env</i> file when initializing the Apollo Client. You can name the environment variable for example <em>APOLLO_URI</em>.
 
-<i>Do not</i> try to access environment variables like <em>process.env.APOLLO_URI</em> outside the <i>app.config.js</i> file. Instead use the <em>Constants.manifest.extra</em> object like in the previous example. In addition, do not import the dotenv library outside the <i>app.config.js</i> file or you will most likely face errors.
+<i>Do not</i> try to access environment variables like <em>process.env.APOLLO_URI</em> outside the <i>app.config.js</i> file. Instead use the <em>Constants.expoConfig.extra</em> object like in the previous example. In addition, do not import the dotenv library outside the <i>app.config.js</i> file or you will most likely face errors.
 
 </div>
 

src/content/10/en/part10d.md

@@ -488,7 +488,7 @@ Now that we have a view for a single repository, let's display repository's revi
 
 Review's <em>text</em> field contains the textual review, <em>rating</em> field a numeric rating between 0 and 100, and <em>createdAt</em> the date when the review was created. Review's <em>user</em> field contains the reviewer's information, which is of type <em>User</em>.
 
-We want to display reviews as a scrollable list, which makes [FlatList](https://reactnative.dev/docs/flatlist) a suitable component for the job. To display the previous exercise's repository's information at the top of the list, you can use the <em>FlatList</em> components [ListHeaderComponent](https://reactnative.dev/docs/flatlist#listheadercomponent) prop. You can use the [ItemSeparatorComponent](https://reactnative.dev/docs/flatlist#itemseparatorcomponent) to add some space between the items like in the <em>RepositoryList</em> component. Here's an example of the structure:
+We want to display reviews as a scrollable list, which makes [FlatList](https://reactnative.dev/docs/flatlist) a suitable component for the job. To display the previous exercise's repository's information at the top of the list, you can use the <em>FlatList</em> component's [ListHeaderComponent](https://reactnative.dev/docs/flatlist#listheadercomponent) prop. You can use the [ItemSeparatorComponent](https://reactnative.dev/docs/flatlist#itemseparatorcomponent) to add some space between the items like in the <em>RepositoryList</em> component. Here's an example of the structure:
 
 ```javascript
 const RepositoryInfo = ({ repository }) => {

src/content/11/en/part11b.md

@@ -225,7 +225,7 @@ The [uses](https://docs.github.com/en/free-pro-team@latest/actions/reference/wor
 
 Here we're using a public action [actions/checkout](https://github.com/actions/checkout) and we specify a version (<code>@v4</code>) to avoid potential breaking changes if the action gets updated. The <code>checkout</code> action does what the name implies: it checkouts the project source code from Git.
 
-Secondly, as the application is written in JavaScript, Node.js must be set up to be able to utilize the commands that are specified in <code>package.json</code>. To set up Node.js, [actions/setup-node](https://github.com/actions/setup-node) action can be used. Version <code>16</code> is selected because it is the version the application is using in the production environment.
+Secondly, as the application is written in JavaScript, Node.js must be set up to be able to utilize the commands that are specified in <code>package.json</code>. To set up Node.js, [actions/setup-node](https://github.com/actions/setup-node) action can be used. Version <code>20</code> is selected because it is the version the application is using in the production environment.
 
 ```yml
 # name and trigger not shown anymore...

src/content/11/en/part11d.md

@@ -292,7 +292,7 @@ When using a third-party action such that <i>github-tag-action</i> it might be a
 
 However, the code in a commit with a particular hash does not change in any circumstances, so if we want to be 100% sure about the code we use, it is safest to use the hash. 
 
-V  ersion [1.61.0](https://github.com/anothrNick/github-tag-action/releases/tag/1.61.0) of the action corresponds to a commit with hash <code>8c8163ef62cf9c4677c8e800f36270af27930f42</code>, so we might want to change our configuration as follows:
+Version [1.61.0](https://github.com/anothrNick/github-tag-action/releases/tag/1.61.0) of the action corresponds to a commit with hash <code>8c8163ef62cf9c4677c8e800f36270af27930f42</code>, so we might want to change our configuration as follows:
 
 ```js
     - name: Bump version and push tag

src/content/2/fi/osa2c.md

@@ -465,7 +465,7 @@ const hook = () => {
 useEffect(hook, [])
 ```
 
-Nyt huomaamme selvemmin, että funktiolle [useEffect]((https://react.dev/reference/react/useEffect) annetaan <i>kaksi parametria</i>. Näistä ensimmäinen on funktio eli itse <i>efekti</i>. Dokumentaation mukaan
+Nyt huomaamme selvemmin, että funktiolle [useEffect](https://react.dev/reference/react/useEffect) annetaan <i>kaksi parametria</i>. Näistä ensimmäinen on funktio eli itse <i>efekti</i>. Dokumentaation mukaan
 
 > <i>By default, effects run after every completed render, but you can choose to fire it only when certain values have changed.</i>
 
@@ -517,7 +517,7 @@ Sovelluksemme kokonaisuuden konfiguraatiosta on pikkuhiljaa muodostunut melko mo
 
 ![](../../images/2/18e.png)
 
-React-sovelluksen muodostavaa JavaScript-koodia siis suoritetaan selaimessa. Selain hakee JavaScriptin <i>React Development Serveriltä</i>, joka on se ohjelma, joka käynnistyy kun suoritetaan komento <em>npm start</em>. Development Server muokkaa sovelluksen JavaScriptin selainta varten sopivaan muotoon, se mm. yhdistelee eri tiedostoissa olevan JavaScript-koodin yhdeksi tiedostoksi. Puhumme enemmän Development Serveristä kurssin [osassa 7](/osa7).
+React-sovelluksen muodostavaa JavaScript-koodia siis suoritetaan selaimessa. Selain hakee JavaScriptin <i>React Development Serveriltä</i>, joka on se ohjelma, joka käynnistyy kun suoritetaan komento <em>npm run dev</em>. Development Server muokkaa sovelluksen JavaScriptin selainta varten sopivaan muotoon, se mm. yhdistelee eri tiedostoissa olevan JavaScript-koodin yhdeksi tiedostoksi. Puhumme enemmän Development Serveristä kurssin [osassa 7](/osa7).
 
 JSON-muodossa olevan datan selaimessa pyörivä React-sovellus hakee siis koneella portissa 3001 käynnissä olevalta JSON Serveriltä, joka taas saa JSON-datan tiedostosta <i>db.json</i>.
 

src/content/3/en/part3a.md

@@ -39,7 +39,7 @@ Let's navigate to an appropriate directory, and create a new template for our ap
 
 The file defines, for instance, that the entry point of the application is the <i>index.js</i> file.
 
-Let's make a small change to the <i>scripts</i> object:
+Let's make a small change to the <i>scripts</i> object by adding a new script command.
 
 ```bash
 {
@@ -154,7 +154,7 @@ import http from 'http'
 
 These days, code that runs in the browser uses ES6 modules. Modules are defined with an [export](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/export) and taken into use with an [import](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/import).
 
-Node.js uses by default so-called [CommonJS](https://en.wikipedia.org/wiki/CommonJS) modules. The reason for this is that the Node ecosystem needed modules long before JavaScript supported them in the language specification. Currently, Node also supports the use of ES6 modules, but since the support is not quite perfect yet, we'll stick to CommonJS modules.
+Node.js uses [CommonJS](https://en.wikipedia.org/wiki/CommonJS) modules. The reason for this is that the Node ecosystem needed modules long before JavaScript supported them in the language specification. Currently, Node also supports the use of ES6 modules, but since the support is not quite perfect yet, we'll stick to CommonJS modules.
 
 CommonJS modules function almost exactly like ES6 modules, at least as far as our needs in this course are concerned.
 
@@ -216,7 +216,7 @@ console.log(`Server running on port ${PORT}`)
 
 Let's restart the server (you can shut the server down by pressing _Ctrl+C_ in the console) and let's refresh the browser.
 
-The <i>application/json</i> value in the <i>Content-Type</i> header informs the receiver that the data is in the JSON format. The _notes_ array gets transformed into JSON with the <em>JSON.stringify(notes)</em> method.
+The <i>application/json</i> value in the <i>Content-Type</i> header informs the receiver that the data is in the JSON format. The _notes_ array gets transformed into JSON formatted string with the <em>JSON.stringify(notes)</em> method. This is necessary because the response.end() method expects a string or a buffer to send as the response body.
 
 When we open the browser, the displayed format is exactly the same as in [part 2](/en/part2/getting_data_from_server/) where we used [json-server](https://github.com/typicode/json-server) to serve the list of notes:
 
@@ -340,7 +340,7 @@ The request is responded to with the [json](http://expressjs.com/en/4x/api.html#
 
 Next, let's take a quick look at the data sent in JSON format.
 
-In the earlier version where we were only using Node, we had to transform the data into the JSON format with the _JSON.stringify_ method:
+In the earlier version where we were only using Node, we had to transform the data into the JSON formatted string with the _JSON.stringify_ method:
 
 ```js
 response.end(JSON.stringify(notes))
@@ -950,7 +950,7 @@ POST is the only HTTP request type that is neither <i>safe</i> nor <i>idempotent
 
 ### Middleware
 
-The express [json-parser](https://expressjs.com/en/api.html) we took into use earlier is a so-called [middleware](http://expressjs.com/en/guide/using-middleware.html).
+The express [json-parser](https://expressjs.com/en/api.html) used earlier is a [middleware](http://expressjs.com/en/guide/using-middleware.html).
 
 Middleware are functions that can be used for handling _request_ and _response_ objects.
 

src/content/3/en/part3c.md

@@ -435,7 +435,8 @@ app.get('/api/notes', (request, response) => {
 
 The code automatically uses the defined _toJSON_ when formatting notes to the response.
 
-### Database configuration into its own module
+### Moving db configuration to its own module
+
 
 Before we refactor the rest of the backend to use the database, let's extract the Mongoose-specific code into its own module.
 

src/content/3/fi/osa3a.md

@@ -337,7 +337,7 @@ Pyyntöön vastataan _response_-olion metodilla [json](http://expressjs.com/en/4
 
 Pieni huomio JSON-muodossa palautettavasta datasta.
 
-Aiemmassa, pelkkää Nodea käyttämässä versiossa, jouduimme muuttamaan palautettavan datan JSON-muotoon metodilla _JSON.stringify_:
+Aiemmassa, pelkkää Nodea käyttävässä versiossa, jouduimme muuttamaan palautettavan datan JSON-muotoon metodilla _JSON.stringify_:
 
 ```js
 response.end(JSON.stringify(notes))

src/content/4/en/part4d.md

@@ -422,7 +422,7 @@ Modify adding new blogs so that it is only possible if a valid token is sent wit
 
 [This example](/en/part4/token_authentication#limiting-creating-new-notes-to-logged-in-users) from part 4 shows taking the token from the header with the _getTokenFrom_ helper function in <i>controllers/blogs.js</i>.
 
-If you used the same solution, refactor taking the token to a [middleware](/en/part3/node_js_and_express#middleware). The middleware should take the token from the <i>Authorization</i> header and place it into the <i>token</i> field of the <i>request</i> object.
+If you used the same solution, refactor taking the token to a [middleware](/en/part3/node_js_and_express#middleware). The middleware should take the token from the <i>Authorization</i> header and assign it to the <i>token</i> field of the <i>request</i> object.
 
 In other words, if you register this middleware in the <i>app.js</i> file before all routes