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practicalli-johnny committed Mar 7, 2024
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Expand Up @@ -8,6 +8,7 @@
- mkdocs: clojure-idiom admonition style
- dev: gitleaks rules configuration for checking secrets in megalinter workflow
- clojure-cli: update donut system and system-repl examples
- reference: code block and admonition for common regular expression examples

# 2024-03-03

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152 changes: 80 additions & 72 deletions docs/reference/standard-library/regular-expressions/common-regex-patterns.md
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Expand Up @@ -12,7 +12,7 @@ A 8 to 24 character passwords that can include any lower case character or digit

Breakdown the regex pattern:

```
```regex
^[a-z0-9_-]{8,24}$
^ # Start of the line
Expand All @@ -33,7 +33,7 @@ The order of the grouping formulas does not matter

Breakdown the regex pattern:

```
```regex
((?=.*\d)(?=.*[a-z])(?=.*[A-Z])(?=.*[@#$%]).{8,24})
( # Start of group
Expand All @@ -58,7 +58,7 @@ The string must start with a `#`symbol , follow by a letter from `a` to `f`, `A`

Breakdown the regex pattern:

```
```regex
^#([A-Fa-f0-9]{3}|[A-Fa-f0-9]{6})$
^ #start of the line
Expand All @@ -83,12 +83,12 @@ The domain starts with `A-Za-z0-9-`, follow by first level domain, e.g `.org`,
"[email protected]")
```

> ####Hint::Double escaping special characters
> Double escaping of special characters is not required in the Clojure syntax.
!!! HINT "Double escaping special characters"
Double escaping of special characters is not required in the Clojure syntax.

Breakdown the regex pattern:

```
```regex
^[_A-Za-z0-9-]+(\\.[_A-Za-z0-9-]+)*@[A-Za-z0-9]+(\\.[A-Za-z0-9]+)*(\\.[A-Za-z]{2,})$
^ #start of the line
Expand Down Expand Up @@ -117,13 +117,14 @@ Change the combination `(jpg|png|gif|bmp)` for other file extension.
(re-matches #"(?i)([^\s]+(\.(jpg|png|gif|bmp))$)" "clojure-logo.png")
```

> #### Hint::in-line modifiers not supported in JavaScript
>
> The REPL above uses ClojureScript, hosted on JavaScript. JavaScript does not support in-line modifier flags such as `(?i)` for a case insensitive pattern. In-line flags will be [converted by the ClojureScript reader if they are the first element in the literal regular expression pattern](https://stackoverflow.com/a/23187290/1762872), or if the `js/RegExp` function is used to create the regular expression.
??? HINT "In-line modifiers indirectly supported in ClojureScript"
ClojureScript is hosted on JavaScript which does not support in-line modifier flags such as `(?i)` for a case insensitive pattern.

In-line flags will be [converted by the ClojureScript reader if they are the first element in the literal regular expression pattern](https://stackoverflow.com/a/23187290/1762872), or if the `js/RegExp` function is used to create the regular expression.

Breakdown the regex pattern:

```
```regex
([^\s]+(\.(?i)(jpg|png|gif|bmp))$)
( #Start of the group #1
Expand Down Expand Up @@ -159,7 +160,7 @@ Example IP address are: `192.168.0.1`, `127.0.0.1`, `192.120.240.100`

Breakdown the regex pattern:

```
```regex
^([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\.([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\.
([01]?\\d\\d?|2[0-4]\\d|25[0-5])\\.([01]?\\d\\d?|2[0-4]\\d|25[0-5])$
Expand Down Expand Up @@ -187,7 +188,7 @@ Time in 12-Hour Format Regular Expression Pattern. The 12-hour clock format sta

Breakdown the regex pattern:

```
```regex
(1[012]|[1-9]):[0-5][0-9](\\s)?(?i)(am|pm)
( #start of group #1
Expand All @@ -212,7 +213,7 @@ The 24-hour clock format start between 0-23 or 00-23, then a semi colon `:` and

Breakdown the regex pattern:

```
```regex
([01]?[0-9]|2[0-3]):[0-5][0-9]
( #start of group #1
Expand All @@ -224,7 +225,7 @@ Breakdown the regex pattern:
[0-5][0-9] # follow by 0..5 and 0..9, which means 00 to 59
```

## Date Format (dd/mm/yyyy) Regular Expression Pattern
## Date Format Pattern

Date format in the form `dd/mm/yyyy`. Validating a leap year and if there is 30 or 31 days in a month is not simple though.

Expand All @@ -234,7 +235,7 @@ Date format in the form `dd/mm/yyyy`. Validating a leap year and if there is 30

Breakdown the regex pattern:

```
```regex
(0?[1-9]|[12][0-9]|3[01])/(0?[1-9]|1[012])/((19|20)\\d\\d)
( #start of group #1
Expand All @@ -256,63 +257,70 @@ Breakdown the regex pattern:
) # end of group #3
```

<!-- ## HTML tag Regular Expression Pattern -->
<!-- HTML code uses tags to define structure of content. HTML tag, start with an opening tag “<" , follow by double quotes "string", or single quotes 'string' but does not allow one double quotes (") "string, one single quote (') 'string or a closing tag > without single or double quotes enclosed. At last , end with a closing tag “>” -->

<!-- ```eval-cloure -->
<!-- (re-matches -->
<!-- #"<("[^"]*"|'[^']*'|[^'">])*>" -->
<!-- "<body><h1>Title</h1><p>Loreum ipsum</p></body>") -->
<!-- ``` -->

<!-- Breakdown the regex pattern: -->
<!-- ``` -->
<!-- <("[^"]*"|'[^']*'|[^'">])*> -->

<!-- < #start with opening tag "<" -->
<!-- ( # start of group #1 -->
<!-- "[^"]*" # only two double quotes are allow - "string" -->
<!-- | # ..or -->
<!-- '[^']*' # only two single quotes are allow - 'string' -->
<!-- | # ..or -->
<!-- [^'">] # cant contains one single quotes, double quotes and ">" -->
<!-- ) # end of group #1 -->
<!-- * # 0 or more -->
<!-- > #end with closing tag ">" -->
<!-- ``` -->

<!-- ## HTML links Regular Expression Pattern -->
<!-- HTML A tag Regular Expression Pattern -->

<!-- (?i)<a([^>]+)>(.+?)</a> -->

<!-- ( #start of group #1 -->
<!-- ?i # all checking are case insensitive -->
<!-- ) #end of group #1 -->
<!-- <a #start with "<a" -->
<!-- ( # start of group #2 -->
<!-- [^>]+ # anything except (">"), at least one character -->
<!-- ) # end of group #2 -->
<!-- > # follow by ">" -->
<!-- (.+?) # match anything -->
<!-- </a> # end with "</a> -->

<!-- ## Extract HTML link Regular Expression Pattern -->

<!-- \s*(?i)href\s*=\s*(\"([^"]*\")|'[^']*'|([^'">\s]+)); -->

<!-- \s* #can start with whitespace -->
<!-- (?i) # all checking are case insensive -->
<!-- href # follow by "href" word -->
<!-- \s*=\s* # allows spaces on either side of the equal sign, -->
<!-- ( # start of group #1 -->
<!-- "([^"]*") # only two double quotes are allow - "string" -->
<!-- | # ..or -->
<!-- '[^']*' # only two single quotes are allow - 'string' -->
<!-- | # ..or -->
<!-- ([^'">]+) # cant contains one single / double quotes and ">" -->
<!-- ) # end of group #1 -->
## HTML tag Pattern

HTML code uses tags to define structure of content. HTML tag, start with an opening tag “<" , follow by double quotes "string", or single quotes 'string' but does not allow one double quotes (") "string, one single quote (') 'string or a closing tag > without single or double quotes enclosed. At last , end with a closing tag “>”

```clojure
(re-matches
#"<("[^"]*"|'[^']*'|[^'">])*>"
"<body><h1>Title</h1><p>Loreum ipsum</p></body>")
```

Breakdown the regex pattern:

```regex
<("[^"]*"|'[^']*'|[^'">])*>

< #start with opening tag "<"
( # start of group #1
"[^"]*" # only two double quotes are allow - "string"
| # ..or
'[^']*' # only two single quotes are allow - 'string'
| # ..or
[^'">] # cant contains one single quotes, double quotes and ">"
) # end of group #1
* # 0 or more
> #end with closing tag ">"
```

## HTML links Regular Expression Pattern

HTML A tag Regular Expression Pattern

```regex
(?i)<a([^>]+)>(.+?)</a>

( #start of group #1
?i # all checking are case insensitive
) #end of group #1
<a #start with "<a"
( # start of group #2
[^>]+ # anything except (">"), at least one character
) # end of group #2
> # follow by ">"
(.+?) # match anything
</a> # end with "</a>
```
## Extract HTML link Regular Expression Pattern
```regex
\s*(?i)href\s*=\s*(\"([^"]*\")|'[^']*'|([^'">\s]+));
\s* #can start with whitespace
(?i) # all checking are case insensive
href # follow by "href" word
\s*=\s* # allows spaces on either side of the equal sign,
( # start of group #1
"([^"]*") # only two double quotes are allow - "string"
| # ..or
'[^']*' # only two single quotes are allow - 'string'
| # ..or
([^'">]+) # cant contains one single / double quotes and ">"
) # end of group #1
```
## Reference
* <https://mkyong.com/regular-expressions/10-java-regular-expression-examples-you-should-know>
* [10 Java regular expression examples](https://mkyong.com/regular-expressions/10-java-regular-expression-examples-you-should-know)

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