https://github.com/nobitagit/regex-reference

a quick regex reference
https://github.com/nobitagit/regex-reference

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a quick regex reference

• Host: GitHub
• URL: https://github.com/nobitagit/regex-reference
• Owner: nobitagit
• Created: 2015-08-06T09:12:38.000Z (over 9 years ago)
• Default Branch: master
• Last Pushed: 2015-08-06T09:59:28.000Z (over 9 years ago)
• Last Synced: 2024-04-14T11:36:31.132Z (9 months ago)
• Size: 121 KB
• Stars: 1
• Watchers: 2
• Forks: 1
• Open Issues: 0
• Metadata Files:
  • Readme: readme.md

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README

        
# Regex reference

A quick regex reference/refresher.

## Flags

`i` - case insensitive.

## Metacharacters

`.` - any char.  

`^` - any starting line.  

`$` - any finishing line.  

`[]` - [character class](classes.md).  

`|` - *or* operator.  

`()` - group `|` (*or*) expressions.  

`?` - the previous char or group is an [optional item](classes.md).  

`\b` - word boundary.  

`?` - match the previous char or group from **0** to a max of **one** time.  

`*` - match the previous char or group from **0** to as many times as possible.  

`+` - match the previous char or group from **1** to as many times as possible.  

`{x,y}` - match the previous char or group from **x** to a max of **y** times.  

# Classes and alternations

Character classes match **one** character among a certain set or range, while aleternations can match more complex cases. While classes have their own set of rules (especially about metacharacters), alternations follow the same rules of a *normal* regex.

Unlike char classes, alternations **can't** be negated.

## Character classes

`[abcde]` - match any of these chars: `a,b,c,d,e`.   

`[a-e]` - match any of these chars: `a,b,c,d,e`.  

`[1-6a-eA-E]` - match ints from `1` through `6`, chars from `a` through `e` (both uppercase and lowercase). Note: `'America'.match(/[a-eA-E]/)` will only match the first A and then stop looking.  

`[a-e!_.?]` - match a range (`a-e`) and the chars `!` `_` `.` and `?`.  

`[-_!]` - note that the dash is **not** always a special char. Here it's matched just like any other char, being at the beginning of the class.  

`[^a-e]` - negate the `a-e` range, i.e. match any char that is **not** in this range.  

## Alternations

`good|bad` - match either the word 'good' or 'bad'.  

`(1|fir)st` - match either 'first' or '1st'.  

`s(up|pid)er(monkey|man)` - match 'spidermonkey', 'supermonkey', 'spiderman', 'superman'.  

`(1[012]|[1-9])` - match either 10, 11, 12 or a single digit number > than 0. (this actually matches the hours of a clock).  

`[0-5][0-9]` - match a two digit number from 00 to 59.  

## Quantifiers

`rams?` - match `ram` and `rams`.  

`spider(man|monkey)?` - matches 'spider', 'spiderman' or 'spidermonkey'.  

`[0-9]+` - match one or more digits.  

`[0-9]*` - match zero or more digits.  

`[0-9]{3,5}` - match 3, 4 or 5 digits.  

## Word boundaries

`\broad\b` - match 'road', discard 'roadside', 'roads', 'broad', 'abroad'.  

`\b[0-9]\b` - match any isolated, one-char number, as in 'I have 1 doubt'.