Merge pull request #2095 from peachesontour/patch-11

Typos

2-ui/99-ui-misc/01-mutation-observer/article.md

@@ -1,7 +1,7 @@
 
 # Mutation observer
 
-`MutationObserver` is a built-in object that observes a DOM element and fires a callback in case of changes.
+`MutationObserver` is a built-in object that observes a DOM element and fires a callback when it detects a change.
 
 We'll first take a look at the syntax, and then explore a real-world use case, to see where such thing may be useful.
 
@@ -128,16 +128,16 @@ Such snippet in an HTML markup looks like this:
 ...
 ```
 
-Also we'll use a JavaScript highlighting library on our site, e.g. [Prism.js](https://prismjs.com/). A call to `Prism.highlightElem(pre)` examines the contents of such `pre` elements and adds into them special tags and styles for colored syntax highlighting, similar to what you see in examples here, at this page.
+For better readability and at the same time, to beautify it, we'll be using a JavaScript syntax highlighting library on our site, like [Prism.js](https://prismjs.com/). To get syntax highlighting for above snippet in Prism, `Prism.highlightElem(pre)` is called, which examines the contents of such `pre` elements and adds special tags and styles for colored syntax highlighting into those elements, similar to what you see in examples here, on this page.
 
-When exactly to run that highlighting method? We can do it on `DOMContentLoaded` event, or at the bottom of the page. At that moment we have our DOM ready, can search for elements `pre[class*="language"]` and call `Prism.highlightElem` on them:
+When exactly should we run that highlighting method? Well, we can do it on `DOMContentLoaded` event, or put the script at the bottom of the page. The moment our DOM is ready, we can search for elements `pre[class*="language"]` and call `Prism.highlightElem` on them:
 
 ```js
 // highlight all code snippets on the page
 document.querySelectorAll('pre[class*="language"]').forEach(Prism.highlightElem);
 ```
 
-Everything's simple so far, right? There are `<pre>` code snippets in HTML, we highlight them.
+Everything's simple so far, right? Where there are `<pre>` code snippets in HTML, we highlight them.
 
 Now let's go on. Let's say we're going to dynamically fetch materials from a server. We'll study methods for that [later in the tutorial](info:fetch). For now it only matters that we fetch an HTML article from a webserver and display it on demand:
 
@@ -162,13 +162,13 @@ snippets.forEach(Prism.highlightElem);
 */!*
 ```
 
-...But imagine, we have many places in the code where we load contents: articles, quizzes, forum posts. Do we need to put the highlighting call everywhere? That's not very convenient, and also easy to forget.
+...But, imagine if we have many places in the code where we load our content - articles, quizzes, forum posts, etc. Do we need to put the highlighting call everywhere? That's not very convenient, right? It is also easy to forget where we put them and therefore, making it harder if we want to make some changes to the code later.
 
-And what if the content is loaded by a third-party module? E.g. we have a forum written by someone else, that loads contents dynamically, and we'd like to add syntax highlighting to it. No one likes to patch third-party scripts.
+And what if the content is loaded by a third-party module? For example, we have a forum written by someone else, that loads content dynamically, and we'd like to add syntax highlighting to it. No one likes patching third-party scripts.
 
 Luckily, there's another option.
 
-We can use `MutationObserver` to automatically detect when code snippets are inserted in the page and highlight them.
+We can use `MutationObserver` to automatically detect when code snippets are inserted into the page and highlight them.
 
 So we'll handle the highlighting functionality in one place, relieving us from the need to integrate it.
 
@@ -236,9 +236,9 @@ There's a method to stop observing the node:
 
 - `observer.disconnect()` -- stops the observation.
 
-When we stop the observing, it might be possible that some changes were not processed by the observer yet.
+When we stop the observing, it might be possible that some changes were not yet processed by the observer. In such cases, we use
 
-- `observer.takeRecords()` -- gets a list of unprocessed mutation records, those that happened, but the callback did not handle them.
+- `observer.takeRecords()` -- gets a list of unprocessed mutation records - those that happened, but the callback has not handled them.
 
 These methods can be used together, like this:
 
@@ -252,14 +252,14 @@ let mutationRecords = observer.takeRecords();
 ```
 
 ```smart header="Garbage collection interaction"
-Observers use weak references to nodes internally. That is: if a node is removed from DOM, and becomes unreachable, then it becomes garbage collected.
+Observers use weak references to nodes internally. That is, if a node is removed from the DOM, and becomes unreachable, then it can be garbage collected.
 
 The mere fact that a DOM node is observed doesn't prevent the garbage collection.
 ```
 
 ## Summary  
 
-`MutationObserver` can react on changes in DOM: attributes, added/removed elements, text content.
+`MutationObserver` can react to changes in DOM - attributes, text content and adding/removing elements.
 
 We can use it to track changes introduced by other parts of our code, as well as to integrate with third-party scripts.