Homogenized images (#69)

* RegExp image for French plus

* Some typo corrected
* Typographics rules (as space before :)
* égual - égal

* Images folder added, img src updated

* § formatted to 80 lines

README-es.md

@@ -21,7 +21,7 @@ Imagina que estas escribiendo una aplicación y quieres agregar reglas para cuan
 
 <br/><br/>
 <p align="center">
-<img src="http://imgur.com/EtlKH14.png" alt="Regular expression">
+  <img src="./img/regexp-es.png" alt="Expresión regular">
 </p>
 
 De la expresión regular anterior, se puede aceptar las cadenas 'john_doe', 'jo-hn_doe' y 'john12_as'. La expresión no coincide con el nombre de usuario 'Jo', porque es una cadena de caracteres que contiene letras mayúsculas y es demasiado corta.

README-fr.md

@@ -24,7 +24,7 @@ le pseudonyme à contenir des lettres, des nombres, des underscores et des trait
 de caractères dans le pseudonyme pour qu'il n'ait pas l'air moche. Nous utilisons l'expression régulière suivante pour valider un pseudonyme:
 <br/><br/>
 <p align="center">
-<img src="http://i.imgur.com/OGM7KV8.png" alt="Expression régulière">
+  <img src="./img/regexp-fr.png" alt="Expressions régulières">
 </p>
 
 L'expression régulière ci-dessus peut accepter les strings `john_doe`, `jo-hn_doe` et `john12_as`. Ça ne fonctionne pas avec `Jo` car

README-ja.md

@@ -27,7 +27,7 @@
 
 <br/><br/>
 <p align="center">
-<img src="https://i.imgur.com/ekFpQUg.png" alt="Regular expression">
+  <img src="./img/regexp-en.png" alt="Regular expression">
 </p>
 
 この正規表現によって `john_doe, jo-hn_doe, john12_as` などは許容されることになります。

README.md

@@ -15,20 +15,26 @@
 
 > Regular expression is a group of characters or symbols which is used to find a specific pattern from a text.
 
-A regular expression is a pattern that is matched against a subject string from left to right. The word "Regular expression" is a
+A regular expression is a pattern that is matched against a subject string from
-mouthful, you will usually find the term abbreviated as "regex" or "regexp". Regular expression is used for replacing a text within
+left to right. The word "Regular expression" is a mouthful, you will usually
-a string, validating form, extract a substring from a string based upon a pattern match, and so much more.
+find the term abbreviated as "regex" or "regexp". Regular expression is used for
+replacing a text within a string, validating form, extract a substring from a
+string based upon a pattern match, and so much more.
+
+Imagine you are writing an application and you want to set the rules for when a
+user chooses their username. We want to allow the username to contain letters,
+numbers, underscores and hyphens. We also want to limit the number of characters
+in username so it does not look ugly. We use the following regular expression to
+validate a username:
 
-Imagine you are writing an application and you want to set the rules for when a user chooses their username. We want to
-allow the username to contain letters, numbers, underscores and hyphens. We also want to limit the number of
-characters in username so it does not look ugly. We use the following regular expression to validate a username:
 <br/><br/>
 <p align="center">
-<img src="https://i.imgur.com/ekFpQUg.png" alt="Regular expression">
+  <img src="./img/regexp-en.png" alt="Regular expression">
 </p>
 
-Above regular expression can accept the strings `john_doe`, `jo-hn_doe` and `john12_as`. It does not match `Jo` because that string
+Above regular expression can accept the strings `john_doe`, `jo-hn_doe` and
-contains uppercase letter and also it is too short.  
+`john12_as`. It does not match `Jo` because that string contains uppercase
+letter and also it is too short.
 
 ## Table of Contents
 
@@ -61,8 +67,9 @@ contains uppercase letter and also it is too short.
 
 ## 1. Basic Matchers
 
-A regular expression is just a pattern of characters that we use to perform search in a text.  For example, the regular expression
+A regular expression is just a pattern of characters that we use to perform
-`the` means: the letter `t`, followed by the letter `h`, followed by the letter `e`.
+search in a text.  For example, the regular expression `the` means: the letter
+`t`, followed by the letter `h`, followed by the letter `e`.
 
 <pre>
 "the" => The fat cat sat on <a href="#learn-regex"><strong>the</strong></a> mat.
@@ -70,9 +77,11 @@ A regular expression is just a pattern of characters that we use to perform sear
 
 [Test the regular expression](https://regex101.com/r/dmRygT/1)
 
-The regular expression `123` matches the string `123`. The regular expression is matched against an input string by comparing each
+The regular expression `123` matches the string `123`. The regular expression is
-character in the regular expression to each character in the input string, one after another. Regular expressions are normally
+matched against an input string by comparing each character in the regular
-case-sensitive so the regular expression `The` would not match the string `the`.
+expression to each character in the input string, one after another. Regular
+expressions are normally case-sensitive so the regular expression `The` would
+not match the string `the`.
 
 <pre>
 "The" => <a href="#learn-regex"><strong>The</strong></a> fat cat sat on the mat.
@@ -82,9 +91,10 @@ case-sensitive so the regular expression `The` would not match the string `the`.
 
 ## 2. Meta Characters
 
-Meta characters are the building blocks of the regular expressions.  Meta characters do not stand for themselves but instead are
+Meta characters are the building blocks of the regular expressions.  Meta
-interpreted in some special way. Some meta characters have a special meaning and are written inside square brackets.
+characters do not stand for themselves but instead are interpreted in some
-The meta characters are as follows:
+special way. Some meta characters have a special meaning and are written inside
+square brackets. The meta characters are as follows:
 
 |Meta character|Description|
 |:----:|----|
@@ -103,9 +113,10 @@ The meta characters are as follows:
 
 ## 2.1 Full stop
 
-Full stop `.` is the simplest example of meta character. The meta character `.` matches any single character. It will not match return 
+Full stop `.` is the simplest example of meta character. The meta character `.`
-or newline characters. For example, the regular expression `.ar` means: any character, followed by the letter `a`, followed by the 
+matches any single character. It will not match return or newline characters.
-letter `r`.
+For example, the regular expression `.ar` means: any character, followed by the
+letter `a`, followed by the letter `r`.
 
 <pre>
 ".ar" => The <a href="#learn-regex"><strong>car</strong></a> <a href="#learn-regex"><strong>par</strong></a>ked in the <a href="#learn-regex"><strong>gar</strong></a>age.
@@ -115,9 +126,11 @@ letter `r`.
 
 ## 2.2 Character set
 
-Character sets are also called character class. Square brackets are used to specify character sets. Use a hyphen inside a character set to
+Character sets are also called character class. Square brackets are used to
-specify the characters' range. The order of the character range inside square brackets doesn't matter. For example, the regular
+specify character sets. Use a hyphen inside a character set to specify the
-expression `[Tt]he` means: an uppercase `T` or lowercase `t`, followed by the letter `h`, followed by the letter `e`.
+characters' range. The order of the character range inside square brackets
+doesn't matter. For example, the regular expression `[Tt]he` means: an uppercase
+`T` or lowercase `t`, followed by the letter `h`, followed by the letter `e`.
 
 <pre>
 "[Tt]he" => <a href="#learn-regex"><strong>The</strong></a> car parked in <a href="#learn-regex"><strong>the</strong></a> garage.
@@ -125,7 +138,9 @@ expression `[Tt]he` means: an uppercase `T` or lowercase `t`, followed by the le
 
 [Test the regular expression](https://regex101.com/r/2ITLQ4/1)
 
-A period inside a character set, however, means a literal period. The regular expression `ar[.]` means: a lowercase character `a`, followed by letter `r`, followed by a period `.` character.
+A period inside a character set, however, means a literal period. The regular
+expression `ar[.]` means: a lowercase character `a`, followed by letter `r`,
+followed by a period `.` character.
 
 <pre>
 "ar[.]" => A garage is a good place to park a c<a href="#learn-regex"><strong>ar.</strong></a>
@@ -135,9 +150,10 @@ A period inside a character set, however, means a literal period. The regular ex
 
 ### 2.2.1 Negated character set
 
-In general, the caret symbol represents the start of the string, but when it is typed after the opening square bracket it negates the
+In general, the caret symbol represents the start of the string, but when it is
-character set. For example, the regular expression `[^c]ar` means: any character except `c`, followed by the character `a`, followed by
+typed after the opening square bracket it negates the character set. For
-the letter `r`.
+example, the regular expression `[^c]ar` means: any character except `c`,
+followed by the character `a`, followed by the letter `r`.
 
 <pre>
 "[^c]ar" => The car <a href="#learn-regex"><strong>par</strong></a>ked in the <a href="#learn-regex"><strong>gar</strong></a>age.
@@ -147,14 +163,17 @@ the letter `r`.
 
 ## 2.3 Repetitions
 
-Following meta characters `+`, `*` or `?` are used to specify how many times a subpattern can occur. These meta characters act
+Following meta characters `+`, `*` or `?` are used to specify how many times a
-differently in different situations.
+subpattern can occur. These meta characters act differently in different
+situations.
 
 ### 2.3.1 The Star
 
-The symbol `*` matches zero or more repetitions of the preceding matcher. The regular expression `a*` means: zero or more repetitions
+The symbol `*` matches zero or more repetitions of the preceding matcher. The
-of preceding lowercase character `a`. But if it appears after a character set or class then it finds the repetitions of the whole
+regular expression `a*` means: zero or more repetitions of preceding lowercase
-character set. For example, the regular expression `[a-z]*` means: any number of lowercase letters in a row.
+character `a`. But if it appears after a character set or class then it finds
+the repetitions of the whole character set. For example, the regular expression
+`[a-z]*` means: any number of lowercase letters in a row.
 
 <pre>
 "[a-z]*" => T<a href="#learn-regex"><strong>he</strong></a> <a href="#learn-regex"><strong>car</strong></a> <a href="#learn-regex"><strong>parked</strong></a> <a href="#learn-regex"><strong>in</strong></a> <a href="#learn-regex"><strong>the</strong></a> <a href="#learn-regex"><strong>garage</strong></a> #21.
@@ -162,10 +181,12 @@ character set. For example, the regular expression `[a-z]*` means: any number of
 
 [Test the regular expression](https://regex101.com/r/7m8me5/1)
 
-The `*` symbol can be used with the meta character `.` to match any string of characters `.*`. The `*` symbol can be used with the
+The `*` symbol can be used with the meta character `.` to match any string of
-whitespace character `\s` to match a string of whitespace characters. For example, the expression `\s*cat\s*` means: zero or more
+characters `.*`. The `*` symbol can be used with the whitespace character `\s`
-spaces, followed by lowercase character `c`, followed by lowercase character `a`, followed by lowercase character `t`, followed by
+to match a string of whitespace characters. For example, the expression
-zero or more spaces.
+`\s*cat\s*` means: zero or more spaces, followed by lowercase character `c`,
+followed by lowercase character `a`, followed by lowercase character `t`,
+followed by zero or more spaces.
 
 <pre>
 "\s*cat\s*" => The fat<a href="#learn-regex"><strong> cat </strong></a>sat on the <a href="#learn-regex">con<strong>cat</strong>enation</a>.
@@ -175,8 +196,10 @@ zero or more spaces.
 
 ### 2.3.2 The Plus
 
-The symbol `+` matches one or more repetitions of the preceding character. For example, the regular expression `c.+t` means: lowercase
+The symbol `+` matches one or more repetitions of the preceding character. For
-letter `c`, followed by at least one character, followed by the lowercase character `t`. It needs to be clarified that `t` is the last `t` in the sentence.
+example, the regular expression `c.+t` means: lowercase letter `c`, followed by
+at least one character, followed by the lowercase character `t`. It needs to be
+clarified that `t` is the last `t` in the sentence.
 
 <pre>
 "c.+t" => The fat <a href="#learn-regex"><strong>cat sat on the mat</strong></a>.
@@ -186,9 +209,11 @@ letter `c`, followed by at least one character, followed by the lowercase charac
 
 ### 2.3.3 The Question Mark
 
-In regular expression the meta character `?` makes the preceding character optional. This symbol matches zero or one instance of
+In regular expression the meta character `?` makes the preceding character
-the preceding character. For example, the regular expression `[T]?he` means: Optional the uppercase letter `T`, followed by the lowercase
+optional. This symbol matches zero or one instance of the preceding character.
-character `h`, followed by the lowercase character `e`.
+For example, the regular expression `[T]?he` means: Optional the uppercase
+letter `T`, followed by the lowercase character `h`, followed by the lowercase
+character `e`.
 
 <pre>
 "[T]he" => <a href="#learn-regex"><strong>The</strong></a> car is parked in the garage.
@@ -204,9 +229,10 @@ character `h`, followed by the lowercase character `e`.
 
 ## 2.4 Braces
 
-In  regular expression braces that are also called quantifiers are used to specify the number of times that a
+In regular expression braces that are also called quantifiers are used to
-character or a group of characters can be repeated. For example, the regular expression `[0-9]{2,3}` means: Match at least 2 digits but not more than 3 (
+specify the number of times that a character or a group of characters can be
-characters in the range of 0 to 9).
+repeated. For example, the regular expression `[0-9]{2,3}` means: Match at least
+2 digits but not more than 3 ( characters in the range of 0 to 9).
 
 <pre>
 "[0-9]{2,3}" => The number was 9.<a href="#learn-regex"><strong>999</strong></a>7 but we rounded it off to <a href="#learn-regex"><strong>10</strong></a>.0.
@@ -214,8 +240,9 @@ characters in the range of 0 to 9).
 
 [Test the regular expression](https://regex101.com/r/juM86s/1)
 
-We can leave out the second number. For example, the regular expression `[0-9]{2,}` means: Match 2 or more digits. If we also remove
+We can leave out the second number. For example, the regular expression
-the comma the regular expression `[0-9]{3}` means: Match exactly 3 digits.
+`[0-9]{2,}` means: Match 2 or more digits. If we also remove the comma the
+regular expression `[0-9]{3}` means: Match exactly 3 digits.
 
 <pre>
 "[0-9]{2,}" => The number was 9.<a href="#learn-regex"><strong>9997</strong></a> but we rounded it off to <a href="#learn-regex"><strong>10</strong></a>.0.
@@ -231,10 +258,13 @@ the comma the regular expression `[0-9]{3}` means: Match exactly 3 digits.
 
 ## 2.5 Character Group
 
-Character group is a group of sub-patterns that is written inside Parentheses `(...)`. As we discussed before that in regular expression
+Character group is a group of sub-patterns that is written inside Parentheses `(...)`.
-if we put a quantifier after a character then it will repeat the preceding character. But if we put quantifier after a character group then
+As we discussed before that in regular expression if we put a quantifier after a
-it repeats the whole character group. For example, the regular expression `(ab)*` matches zero or more repetitions of the character "ab".
+character then it will repeat the preceding character. But if we put quantifier
-We can also use the alternation `|` meta character inside character group. For example, the regular expression `(c|g|p)ar` means: lowercase character `c`,
+after a character group then it repeats the whole character group. For example,
+the regular expression `(ab)*` matches zero or more repetitions of the character
+"ab". We can also use the alternation `|` meta character inside character group.
+For example, the regular expression `(c|g|p)ar` means: lowercase character `c`,
 `g` or `p`, followed by character `a`, followed by character `r`.
 
 <pre>
@@ -245,11 +275,15 @@ We can also use the alternation `|` meta character inside character group. For e
 
 ## 2.6 Alternation
 
-In regular expression Vertical bar `|` is used to define alternation. Alternation is like a condition between multiple expressions. Now,
+In regular expression Vertical bar `|` is used to define alternation.
-you may be thinking that character set and alternation works the same way. But the big difference between character set and alternation
+Alternation is like a condition between multiple expressions. Now, you may be
-is that character set works on character level but alternation works on expression level. For example, the regular expression
+thinking that character set and alternation works the same way. But the big
-`(T|t)he|car` means: uppercase character `T` or lowercase `t`, followed by lowercase character `h`, followed by lowercase character `e`
+difference between character set and alternation is that character set works on
-or lowercase character `c`, followed by lowercase character `a`, followed by lowercase character `r`.
+character level but alternation works on expression level. For example, the
+regular expression `(T|t)he|car` means: uppercase character `T` or lowercase
+`t`, followed by lowercase character `h`, followed by lowercase character `e` or
+lowercase character `c`, followed by lowercase character `a`, followed by
+lowercase character `r`.
 
 <pre>
 "(T|t)he|car" => <a href="#learn-regex"><strong>The</strong></a> <a href="#learn-regex"><strong>car</strong></a> is parked in <a href="#learn-regex"><strong>the</strong></a> garage.
@@ -259,12 +293,16 @@ or lowercase character `c`, followed by lowercase character `a`, followed by low
 
 ## 2.7 Escaping special character
 
-Backslash `\` is used in regular expression to escape the next character. This allows us to specify a symbol as a matching character 
+Backslash `\` is used in regular expression to escape the next character. This
-including reserved characters `{ } [ ] / \ + * . $ ^ | ?`. To use a special character as a matching character prepend `\` before it. 
+allows us to specify a symbol as a matching character including reserved
+characters `{ } [ ] / \ + * . $ ^ | ?`. To use a special character as a matching
+character prepend `\` before it.
 
-For example, the regular expression `.` is used to match any character except newline. Now to match `.` in an input string the regular
+For example, the regular expression `.` is used to match any character except
-expression `(f|c|m)at\.?` means: lowercase letter `f`, `c` or `m`, followed by lowercase character `a`, followed by lowercase letter 
+newline. Now to match `.` in an input string the regular expression
-`t`, followed by optional `.` character.
+`(f|c|m)at\.?` means: lowercase letter `f`, `c` or `m`, followed by lowercase
+character `a`, followed by lowercase letter `t`, followed by optional `.`
+character.
 
 <pre>
 "(f|c|m)at\.?" => The <a href="#learn-regex"><strong>fat</strong></a> <a href="#learn-regex"><strong>cat</strong></a> sat on the <a href="#learn-regex"><strong>mat.</strong></a>
@@ -274,18 +312,22 @@ expression `(f|c|m)at\.?` means: lowercase letter `f`, `c` or `m`, followed by l
 
 ## 2.8 Anchors
 
-In regular expressions, we use anchors to check if the matching symbol is the starting symbol or ending symbol of the
+In regular expressions, we use anchors to check if the matching symbol is the
-input string. Anchors are of two types: First type is Caret `^` that check if the matching character is the start
+starting symbol or ending symbol of the input string. Anchors are of two types:
-character of the input and the second type is Dollar `$` that checks if matching character is the last character of the
+First type is Caret `^` that check if the matching character is the start
-input string.
+character of the input and the second type is Dollar `$` that checks if matching
+character is the last character of the input string.
 
 ### 2.8.1 Caret
 
-Caret `^` symbol is used to check if matching character is the first character of the input string. If we apply the following regular
+Caret `^` symbol is used to check if matching character is the first character
-expression `^a` (if a is the starting symbol) to input string `abc` it matches `a`. But if we apply regular expression `^b` on above
+of the input string. If we apply the following regular expression `^a` (if a is
-input string it does not match anything. Because in input string `abc` "b" is not the starting symbol. Let's take a look at another
+the starting symbol) to input string `abc` it matches `a`. But if we apply
-regular expression `^(T|t)he` which means: uppercase character `T` or lowercase character `t` is the start symbol of the input string,
+regular expression `^b` on above input string it does not match anything.
-followed by lowercase character `h`, followed by lowercase character `e`.
+Because in input string `abc` "b" is not the starting symbol. Let's take a look
+at another regular expression `^(T|t)he` which means: uppercase character `T` or
+lowercase character `t` is the start symbol of the input string, followed by
+lowercase character `h`, followed by lowercase character `e`.
 
 <pre>
 "(T|t)he" => <a href="#learn-regex"><strong>The</strong></a> car is parked in <a href="#learn-regex"><strong>the</strong></a> garage.
@@ -301,9 +343,10 @@ followed by lowercase character `h`, followed by lowercase character `e`.
 
 ### 2.8.2 Dollar
 
-Dollar `$` symbol is used to check if matching character is the last character of the input string. For example, regular expression
+Dollar `$` symbol is used to check if matching character is the last character
-`(at\.)$` means: a lowercase character `a`, followed by lowercase character `t`, followed by a `.` character and the matcher
+of the input string. For example, regular expression `(at\.)$` means: a
-must be end of the string.
+lowercase character `a`, followed by lowercase character `t`, followed by a `.`
+character and the matcher must be end of the string.
 
 <pre>
 "(at\.)" => The fat c<a href="#learn-regex"><strong>at.</strong></a> s<a href="#learn-regex"><strong>at.</strong></a> on the m<a href="#learn-regex"><strong>at.</strong></a>
@@ -319,8 +362,9 @@ must be end of the string.
 
 ##  3. Shorthand Character Sets
 
-Regular expression provides shorthands for the commonly used character sets, which offer convenient shorthands for commonly used
+Regular expression provides shorthands for the commonly used character sets,
-regular expressions. The shorthand character sets are as follows:
+which offer convenient shorthands for commonly used regular expressions. The
+shorthand character sets are as follows:
 
 |Shorthand|Description|
 |:----:|----|
@@ -334,11 +378,15 @@ regular expressions. The shorthand character sets are as follows:
 
 ## 4. Lookaround
 
-Lookbehind and lookahead sometimes known as lookaround are specific type of ***non-capturing group*** (Use to match the pattern but not
+Lookbehind and lookahead sometimes known as lookaround are specific type of
-included in matching list). Lookaheads are used when we have the condition that this pattern is preceded or followed by another certain
+***non-capturing group*** (Use to match the pattern but not included in matching
-pattern. For example, we want to get all numbers that are preceded by `$` character from the following input string `$4.44 and $10.88`.
+list). Lookaheads are used when we have the condition that this pattern is
-We will use following regular expression `(?<=\$)[0-9\.]*` which means: get all the numbers which contain `.` character and  are preceded
+preceded or followed by another certain pattern. For example, we want to get all
-by `$` character. Following are the lookarounds that are used in regular expressions:
+numbers that are preceded by `$` character from the following input string
+`$4.44 and $10.88`. We will use following regular expression `(?<=\$)[0-9\.]*`
+which means: get all the numbers which contain `.` character and  are preceded
+by `$` character. Following are the lookarounds that are used in regular
+expressions:
 
 |Symbol|Description|
 |:----:|----|
@@ -349,12 +397,16 @@ by `$` character. Following are the lookarounds that are used in regular express
 
 ### 4.1 Positive Lookahead
 
-The positive lookahead asserts that the first part of the expression must be followed by the lookahead expression. The returned match
+The positive lookahead asserts that the first part of the expression must be
-only contains the text that is matched by the first part of the expression. To define a positive lookahead, parentheses are used. Within
+followed by the lookahead expression. The returned match only contains the text
-those parentheses, a question mark with equal sign is used like this: `(?=...)`. Lookahead expression is written after the equal sign inside
+that is matched by the first part of the expression. To define a positive
-parentheses. For example, the regular expression `[T|t]he(?=\sfat)` means: optionally match lowercase letter `t` or uppercase letter `T`,
+lookahead, parentheses are used. Within those parentheses, a question mark with
-followed by letter `h`, followed by letter `e`. In parentheses we define positive lookahead which tells regular expression engine to match
+equal sign is used like this: `(?=...)`. Lookahead expression is written after
-`The` or `the` which are followed by the word `fat`.
+the equal sign inside parentheses. For example, the regular expression
+`[T|t]he(?=\sfat)` means: optionally match lowercase letter `t` or uppercase
+letter `T`, followed by letter `h`, followed by letter `e`. In parentheses we
+define positive lookahead which tells regular expression engine to match `The`
+or `the` which are followed by the word `fat`.
 
 <pre>
 "[T|t]he(?=\sfat)" => <a href="#learn-regex"><strong>The</strong></a> fat cat sat on the mat.
@@ -364,10 +416,13 @@ followed by letter `h`, followed by letter `e`. In parentheses we define positiv
 
 ### 4.2 Negative Lookahead
 
-Negative lookahead is used when we need to get all matches from input string that are not followed by a pattern. Negative lookahead
+Negative lookahead is used when we need to get all matches from input string
-defined same as we define positive lookahead but the only difference is instead of equal `=` character we use negation `!` character
+that are not followed by a pattern. Negative lookahead defined same as we define
-i.e. `(?!...)`. Let's take a look at the following regular expression `[T|t]he(?!\sfat)` which means: get all `The` or `the` words from
+positive lookahead but the only difference is instead of equal `=` character we
-input string that are not followed by the word `fat` precedes by a space character.
+use negation `!` character i.e. `(?!...)`. Let's take a look at the following
+regular expression `[T|t]he(?!\sfat)` which means: get all `The` or `the` words
+from input string that are not followed by the word `fat` precedes by a space
+character.
 
 <pre>
 "[T|t]he(?!\sfat)" => The fat cat sat on <a href="#learn-regex"><strong>the</strong></a> mat.
@@ -377,9 +432,10 @@ input string that are not followed by the word `fat` precedes by a space charact
 
 ### 4.3 Positive Lookbehind
 
-Positive lookbehind is used to get all the matches that are preceded by a specific pattern. Positive lookbehind is denoted by
+Positive lookbehind is used to get all the matches that are preceded by a
-`(?<=...)`. For example, the regular expression `(?<=[T|t]he\s)(fat|mat)` means: get all `fat` or `mat` words from input string that
+specific pattern. Positive lookbehind is denoted by `(?<=...)`. For example, the
-are after the word `The` or `the`.
+regular expression `(?<=[T|t]he\s)(fat|mat)` means: get all `fat` or `mat` words
+from input string that are after the word `The` or `the`.
 
 <pre>
 "(?<=[T|t]he\s)(fat|mat)" => The <a href="#learn-regex"><strong>fat</strong></a> cat sat on the <a href="#learn-regex"><strong>mat</strong></a>.
@@ -389,9 +445,10 @@ are after the word `The` or `the`.
 
 ### 4.4 Negative Lookbehind
 
-Negative lookbehind is used to get all the matches that are not preceded by a specific pattern. Negative lookbehind is denoted by
+Negative lookbehind is used to get all the matches that are not preceded by a
-`(?<!...)`. For example, the regular expression `(?<!(T|t)he\s)(cat)` means: get all `cat` words from input string that
+specific pattern. Negative lookbehind is denoted by `(?<!...)`. For example, the
-are not after the word `The` or `the`.
+regular expression `(?<!(T|t)he\s)(cat)` means: get all `cat` words from input
+string that are not after the word `The` or `the`.
 
 <pre>
 "(?&lt;![T|t]he\s)(cat)" => The cat sat on <a href="#learn-regex"><strong>cat</strong></a>.
@@ -401,8 +458,9 @@ are not after the word `The` or `the`.
 
 ## 5. Flags
 
-Flags are also called modifiers because they modify the output of a regular expression. These flags can be used in any order or
+Flags are also called modifiers because they modify the output of a regular
-combination, and are an integral part of the RegExp.
+expression. These flags can be used in any order or combination, and are an
+integral part of the RegExp.
 
 |Flag|Description|
 |:----:|----|
@@ -412,10 +470,12 @@ combination, and are an integral part of the RegExp.
 
 ### 5.1 Case Insensitive
 
-The `i` modifier is used to perform case-insensitive matching. For example, the regular expression `/The/gi` means: uppercase letter
+The `i` modifier is used to perform case-insensitive matching. For example, the
-`T`, followed by lowercase character `h`, followed by character `e`. And at the end of regular expression the `i` flag tells the
+regular expression `/The/gi` means: uppercase letter `T`, followed by lowercase
-regular expression engine to ignore the case. As you can see we also provided `g` flag because we want to search for the pattern in
+character `h`, followed by character `e`. And at the end of regular expression
-the whole input string.
+the `i` flag tells the regular expression engine to ignore the case. As you can
+see we also provided `g` flag because we want to search for the pattern in the
+whole input string.
 
 <pre>
 "The" => <a href="#learn-regex"><strong>The</strong></a> fat cat sat on the mat.
@@ -431,10 +491,11 @@ the whole input string.
 
 ### 5.2 Global search
 
-The `g` modifier is used to perform a global match (find all matches rather than stopping after the first match). For example, the
+The `g` modifier is used to perform a global match (find all matches rather than
-regular expression`/.(at)/g` means: any character except new line, followed by lowercase character `a`, followed by lowercase
+stopping after the first match). For example, the regular expression`/.(at)/g`
-character `t`. Because we provided `g` flag at the end of the regular expression now it will find every matches from whole input
+means: any character except new line, followed by lowercase character `a`,
-string.
+followed by lowercase character `t`. Because we provided `g` flag at the end of
+the regular expression now it will find every matches from whole input string.
 
 <pre>
 "/.(at)/" => The <a href="#learn-regex"><strong>fat</strong></a> cat sat on the mat.
@@ -450,10 +511,13 @@ string.
 
 ### 5.3 Multiline
 
-The `m` modifier is used to perform a multi-line match. As we discussed earlier anchors `(^, $)` are used to check if pattern is
+The `m` modifier is used to perform a multi-line match. As we discussed earlier
-the beginning of the input or end of the input string. But if we want that anchors works on each line we use `m` flag. For example, the
+anchors `(^, $)` are used to check if pattern is the beginning of the input or
-regular expression `/at(.)?$/gm` means: lowercase character `a`, followed by lowercase character `t`, optionally anything except new
+end of the input string. But if we want that anchors works on each line we use
-line. And because of `m` flag now regular expression engine matches pattern at the end of each line in a string.
+`m` flag. For example, the regular expression `/at(.)?$/gm` means: lowercase
+character `a`, followed by lowercase character `t`, optionally anything except
+new line. And because of `m` flag now regular expression engine matches pattern
+at the end of each line in a string.
 
 <pre>
 "/.at(.)?$/" => The fat