The design is very human

[midnitte@beehaw.org]

The downsides are having to relearn it every time you need to understand it.

[satyrsack@lemmy.sdf.org]

Here is my cheatsheet that has been very helpful. Obviously, this will not teach you how RegEx works, but is a good quick reference when I forget the exact syntax for something.

RegExp

Character classes

Pattern	Description
.	Any character, except newline
\w	Word
\d	Digit
\s	Whitespace
\W	Not word
\D	Not digit
\S	Not whitespace
[abc]	Any of a, b, or c
[a-e]	Characters between a and e
[1-9]	Digit between 1 and 9
[[:print:]]	Any printable character including spaces
[^abc]	Any character except a, b or c

Anchors

Pattern	Description
\G	Start of match
^	Start of string *
$	End of string *
\A	Start of string
\Z	End of string
\z	Absolute end of string
\b	A word boundary
\B	Non-word boundary
^abc	Start with abc
abc$	End with abc

For multiline patterns (m flag), ^ and $ will act as start and end of line.

Escaped characters

Pattern	Description
\. \* \\	Escape special character used by regex
\t	Tab
\n	Newline
\r	Carriage return

Groups

Pattern	Description
(abc)	Capture group
(a\|b)	Match a or b
(?:abc)	Match abc, but don't capture
\1	Substituted with text matched of the 1st capturing group

Quantifiers

Pattern	Description
a*	Match 0 or more
a+	Match 1 or more
a?	Match 0 or 1
a{5}	Match exactly 5
a{,3}	Match up to 3
a{3,}	Match 3 or more
a{1,3}	Match between 1 and 3

Lookahead & Lookbehind

Pattern	Description
a(?=b)	Match a in baby but not in bay
a(?!b)	Match a in Stan but not in Stab
(?<=a)b	Match b in crabs but not in cribs
(?<!a)b	Match b in fib but not in fab
(?<![a-z])abc(?![a-z])	Match abc without any letters before/after

::: spoiler Raw Markdown

# RegExp

## Character classes

| Pattern       | Description                              |
| ------------- | ---------------------------------------- |
| `.`           | Any character, except newline            |
| `\w`          | Word                                     |
| `\d`          | Digit                                    |
| `\s`          | Whitespace                               |
| `\W`          | Not word                                 |
| `\D`          | Not digit                                |
| `\S`          | Not whitespace                           |
| `[abc]`       | Any of a, b, or c                        |
| `[a-e]`       | Characters between `a` and `e`           |
| `[1-9]`       | Digit between `1` and `9`                |
| `[[:print:]]` | Any printable character including spaces |
| `[^abc]`      | Any character except `a`, `b` or `c`     |

## Anchors

| Pattern | Description            |
| ------- | ---------------------- |
| `\G`    | Start of match         |
| `^`     | Start of string \*     |
| `$`     | End of string \*       |
| `\A`    | Start of string        |
| `\Z`    | End of string          |
| `\z`    | Absolute end of string |
| `\b`    | A word boundary        |
| `\B`    | Non-word boundary      |
| `^abc`  | Start with `abc`       |
| `abc$`  | End with `abc`         |

For multiline patterns (`m` flag), `^` and `$` will act as start and end of line.

## Escaped characters

| Pattern    | Description                            |
| ---------- | -------------------------------------- |
| `\. \* \\` | Escape special character used by regex |
| `\t`       | Tab                                    |
| `\n`       | Newline                                |
| `\r`       | Carriage return                        |

## Groups

| Pattern   | Description                                              |
| --------- | -------------------------------------------------------- |
| `(abc)`   | Capture group                                            |
| `(a\|b)`  | Match `a` or `b`                                         |
| `(?:abc)` | Match `abc`, but don't capture                           |
| `\1`      | Substituted with text matched of the 1st capturing group |


## Quantifiers

| Pattern  | Description           |
| -------- | --------------------- |
| `a*`     | Match 0 or more       |
| `a+`     | Match 1 or more       |
| `a?`     | Match 0 or 1          |
| `a{5}`   | Match exactly 5       |
| `a{,3}`  | Match up to 3         |
| `a{3,}`  | Match 3 or more       |
| `a{1,3}` | Match between 1 and 3 |

## Lookahead & Lookbehind

| Pattern                  | Description                                  |
| ---                      | ---                                          |
| `a(?=b)`                 | Match `a` in `baby` but not in `bay`         |
| `a(?!b)`                 | Match `a` in `Stan` but not in `Stab`        |
| `(?<=a)b`                | Match `b` in `crabs` but not in `cribs`      |
| `(?<!a)b`                | Match `b` in `fib` but not in `fab`          |
| `(?<![a-z])abc(?![a-z])` | Match `abc` without any letters before/after |

:::

[tgirlschierke@lemmy.blahaj.zone]

yandev is that you

[yaroto98@lemmy.org]

Jr developer told to sanitize inputs to keep db secure. Comes up with this.

[mkwt@lemmy.world]

One time I did this thing with an internal calibration program where the user had to type floats into a text box. I set it up so that every key stroke was validated so that the string in the box had to parse as a valid number within the assigned range at all intermediate steps.

Everyone hated that.

[goatbeard@beehaw.org]

Just use something like https://regex101.com/

[madcaesar@lemmy.world]

That's not the front-end job. You can do common sense stuff, but any real protection needs to be on the backend. Any front end validation is basically "plz don't hax"

[mormegil@programming.dev]

Add automatic normalization to the box (you know, you type "05" and it drops the leading zero, you type "0.70" and it drops the trailing zero, etc.) and it often gets completely impossible to write anything valid. Some banking apps do something similar.

[matty_r@programming.dev]

Frontend validation is for real time user feedback (without hitting the backend constantly) instead of needing to submit the form before throwing an error/warning.

[zqwzzle@lemmy.ca]

https://imgur.com/a/S0ZVG1T