minor fixes

1-js/04-object-basics/07-optional-chaining/article.md

@@ -32,7 +32,7 @@ In many practical cases we'd prefer to get `undefined` instead of an error here
 let html = document.querySelector('.elem').innerHTML; // error if it's null
 ```
 
-Once again, if the element doesn't exist, we'll get an error accessing `.innerHTML` of `null`. And in some cases, when the absence of the element is normal, we'd like to avoid the error and just accept `html = null` as the result.
+Once again, if the element doesn't exist, we'll get an error accessing `.innerHTML` property of `null`. And in some cases, when the absence of the element is normal, we'd like to avoid the error and just accept `html = null` as the result.
 
 How can we do this?
 
@@ -44,11 +44,19 @@ let user = {};
 alert(user.address ? user.address.street : undefined);
 ```
 
-It works, there's no error... But it's quite inelegant. As you can see, the `"user.address"` appears twice in the code. For more deeply nested properties, that becomes a problem as more repetitions are required.
+It works, there's no error... But it's quite inelegant. As you can see, the `"user.address"` appears twice in the code.
 
-E.g. let's try getting `user.address.street.name`.
+Here's how the same would look for `document.querySelector`:
 
-We need to check both `user.address` and `user.address.street`:
+```js run
+let html = document.querySelector('.elem') ? document.querySelector('.elem').innerHTML : null;
+```
+
+We can see that the element search `document.querySelector('.elem')` is actually called twice here. Not good.
+
+For more deeply nested properties, it becomes even uglier, as more repetitions are required.
+
+E.g. let's get `user.address.street.name` in a similar fashion.
 
 ```js
 let user = {}; // user has no address
@@ -58,7 +66,7 @@ alert(user.address ? user.address.street ? user.address.street.name : null : nul
 
 That's just awful, one may even have problems understanding such code.
 
-Don't even care to, as there's a better way to write it, using the `&&` operator:
+There's a little better way to write it, using the `&&` operator:
 
 ```js run
 let user = {}; // user has no address
@@ -92,6 +100,12 @@ alert( user?.address?.street ); // undefined (no error)
 
 The code is short and clean, there's no duplication at all.
 
+Here's an example with `document.querySelector`:
+
+```js run
+let html = document.querySelector('.elem')?.innerHTML; // will be null, if there's no element
+```
+
 Reading the address with `user?.address` works even if `user` object doesn't exist:
 
 ```js run
@@ -162,11 +176,11 @@ userAdmin.admin?.(); // I am admin
 */!*
 
 *!*
-userGuest.admin?.(); // nothing (no such method)
+userGuest.admin?.(); // nothing happens (no such method)
 */!*
 ```
 
-Here, in both lines we first use the dot (`userAdmin.admin`) to get `admin` property, because we assume that the user object exists, so it's safe read from it.
+Here, in both lines we first use the dot (`userAdmin.admin`) to get `admin` property, because we assume that the `user` object exists, so it's safe read from it.
 
 Then `?.()` checks the left part: if the admin function exists, then it runs (that's so for `userAdmin`). Otherwise (for `userGuest`) the evaluation stops without errors.
 
@@ -199,10 +213,9 @@ For example:
 let user = null;
 
 user?.name = "John"; // Error, doesn't work
-// because it evaluates to undefined = "John"
+// because it evaluates to: undefined = "John"
 ```
 
-It's just not that smart.
 ````
 
 ## Summary
@@ -217,4 +230,4 @@ As we can see, all of them are straightforward and simple to use. The `?.` check
 
 A chain of `?.` allows to safely access nested properties.
 
-Still, we should apply `?.` carefully, only where it's acceptable that the left part doesn't exist. So that it won't hide programming errors from us, if they occur.
+Still, we should apply `?.` carefully, only where it's acceptable, according to our code logic, that the left part doesn't exist. So that it won't hide programming errors from us, if they occur.