minor

9-regular-expressions/01-regexp-introduction/article.md

@@ -1,10 +1,16 @@
 # Patterns and flags
 
+Regular expressions is a powerful way to search and replace in text.
+
+In JavaScript, they are available as `RegExp` object, and also integrated in methods of strings.
+
+## Regular Expressions
+
 A regular expression (also "regexp", or just "reg") consists of a *pattern* and optional *flags*.
 
 There are two syntaxes to create a regular expression object.
 
-The long syntax:
+The "long" syntax:
 
 ```js
 regexp = new RegExp("pattern", "flags");

9-regular-expressions/03-regexp-character-classes/article.md

@@ -89,9 +89,11 @@ When regular expression engine is doing the search, it's moving along the string
 
 When the pattern contains `pattern:\b`, it tests that the position in string is a word boundary, that is one of three variants:
 
-- Immediately before is `\w`, and immediately after -- not `\w`, or vise versa.
-- At string start, and the first string character is `\w`.
-- At string end, and the last string character is `\w`.
+There are three different positions that qualify as word boundaries:
+
+- At string start, if the first string character is a word character `\w`.
+- Between two characters in the string, where one is a word character `\w` and the other is not.
+- At string end, if the last string character is a word character `\w`.
 
 For instance, in the string `subject:Hello, Java!` the following positions match `\b`:
 
@@ -101,11 +103,10 @@ So it matches `pattern:\bHello\b`, because:
 
 1. At the beginning of the string the first `\b` test matches.
 2. Then the word `Hello` matches.
-3. Then `\b` matches, as we're between `o` and a space.
+3. Then `\b` matches, as we're between `o` (a word character) and a space (not a word character).
 
 Pattern `pattern:\bJava\b` also matches. But not `pattern:\bHell\b` (because there's no word boundary after `l`) and not `Java!\b` (because the exclamation sign is not a wordly character, so there's no word boundary after it).
 
-
 ```js run
 alert( "Hello, Java!".match(/\bHello\b/) ); // Hello
 alert( "Hello, Java!".match(/\bJava\b/) );  // Java