minor fixes

iliakan · iliakan · commit 6384ccba054f · 2020-01-19T20:32:27.000+01:00
diff --git a/1-js/05-data-types/07-map-set/article.md b/1-js/05-data-types/07-map-set/article.md
@@ -41,6 +41,12 @@ alert( map.size ); // 3
 
 As we can see, unlike objects, keys are not converted to strings. Any type of key is possible.
 
+```smart header="`map[key]` isn't the right way to use a `Map`"
+Although `map[key]` also works, e.g. we can set `map[key] = 2`, this is treating `map` as a plain JavaScript object, so it implies all corresponding limitations (no object keys and so on).
+
+So we should use `map` methods: `set`, `get` and so on.
+```
+
 **Map can also use objects as keys.**
 
 For instance:
diff --git a/9-regular-expressions/14-regexp-lookahead-lookbehind/2-insert-after-head/solution.md b/9-regular-expressions/14-regexp-lookahead-lookbehind/2-insert-after-head/solution.md
@@ -1,18 +1,19 @@
-In order to insert after the `<body>` tag, you must first find it. We will use the regular expression pattern `pattern:<body.*>`.
+In order to insert after the `<body>` tag, we must first find it. We can use the regular expression pattern `pattern:<body.*>` for that.
 
-Next, we need to leave the `<body>` tag in place and add text after it.
+In this task we don't need to modify the `<body>` tag. We only need to add the text after it.
+
+Here's how we can do it:
 
-This can be done like this:
 ```js run
 let str = '...<body style="...">...';
 str = str.replace(/<body.*>/, '$&<h1>Hello</h1>');
 
 alert(str); // ...<body style="..."><h1>Hello</h1>...
 ```
 
-In the replacement string `$&` means the match itself, that is, we replace `pattern:<body.*>` Is replaced by itself plus  `<h1>Hello</h1>`.
+In the replacement string `$&` means the match itself, that is, the part of the source text that corresponds to `pattern:<body.*>`. It gets replaced by itself plus `<h1>Hello</h1>`.
 
-An alternative is to use retrospective validation:
+An alternative is to use lookbehind:
 
 ```js run
 let str = '...<body style="...">...';
@@ -21,8 +22,15 @@ str = str.replace(/(?<=<body.*>)/, `<h1>Hello</h1>`);
 alert(str); // ...<body style="..."><h1>Hello</h1>...
 ```
 
-Such a regular expression at each position will check if `pattern:<body.*>`does not go directly in front of it. If yes, a match is found. But the tag `pattern:<body.*>` does not coincide, it only participates in the verification. And there are no other characters after checking in it, so the match text will be empty.
+As you can see, there's only lookbehind part in this regexp.
+
+It works like this:
+- At every position in the text.
+- Check if it's preceeded by `pattern:<body.*>`.
+- If it's so then we have the match.
+
+The tag `pattern:<body.*>` won't be returned. The result of this regexp is literally an empty string, but it matches only at positions preceeded by `pattern:<body.*>`.
 
-This replaces the "empty line", followed by `pattern:<body.*>` With `<h1>Hello</h1>`. Which, exactly, is the insertion of this line after `<body>`.
+So we replaces the "empty line", preceeded by `pattern:<body.*>`, with `<h1>Hello</h1>`. That's the insertion after `<body>`.
 
-P.S. The flags: `pattern:/<body.*>/si`, will not interfere with this regular expression, so that a line break appears in the "dot" (a tag can span several lines), and also that the tags are in a different register of the `match:<BODY>` type, too.
+P.S. Regexp flags, such as `pattern:s` and `pattern:i` can also useful: `pattern:/<body.*>/si`. The `pattern:s` flag makes the dot `pattern:.` match a newline character, and `pattern:i` flag makes `pattern:<body>` also match `match:<BODY>` case-insensitively.
diff --git a/9-regular-expressions/14-regexp-lookahead-lookbehind/2-insert-after-head/task.md b/9-regular-expressions/14-regexp-lookahead-lookbehind/2-insert-after-head/task.md
@@ -1,8 +1,8 @@
 # Insert After Head
 
-There is a line with an HTML Document.
+We have a string with an HTML Document.
 
-Insert after tag `<body>` (it may have attributes) line `<h1>Hello</h1>`.
+Write a regular expression that inserts `<h1>Hello</h1>` immediately after `<body>` tag. The tag may have attributes.
 
 For instance:
 
@@ -20,7 +20,7 @@ let str = `
 str = str.replace(regexp, `<h1>Hello</h1>`);
 ```
 
-After that value `str`:
+After that the value of `str` should be:
 ```html
 <html>
   <body style="height: 200px"><h1>Hello</h1>
