64 lines
2.4 KiB
Markdown
64 lines
2.4 KiB
Markdown
---
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title: Regular Expressions Cheat Sheet
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type: cheatsheet
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tags: javascript,string,regexp,cheatsheet
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expertise: beginner
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author: chalarangelo
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cover: blog_images/tools.jpg
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excerpt: Regular expressions are a very useful tool in a variety of situations. Save this cheatsheet for any time you need to look up their syntax and speed up your development.
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firstSeen: 2020-05-01T15:39:07+03:00
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lastUpdated: 2021-06-12T19:30:41+03:00
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---
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### Anchors
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- `^`: start of the string or the start of a line in a multiline pattern
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- `$`: end of the string or the end of a line in a multiline pattern
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- `\b`: word boundary
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- `\B`: not word boundary (opposite of `\b`)
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Note: Anchors are non-quantifiable (i.e. cannot be followed by a quantifier).
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### Character sequences
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- `.`: any character except line breaks
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- `\w`: any word character
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- `\W`: any non-word character (opposite of `\w`)
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- `\s`: any whitespace character
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- `\S`: any non-whitespace character (opposite of `\s`)
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- `\d`: any digit character
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- `\D`: any non-digit character (opposite of `\d`)
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- `[abc]`: a single character in the given set (here `a`, `b` or `c`)
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- `[^abc]`: a single character not in the given set (opposite of `[abc]`)
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- `[a-z]`: a single character in the given range (here between `a` and `z` inclusive)
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- `[^a-z]`: a single character not in the given range (opposite of `[a-z]`)
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- `[a-zA-Z]`: a single character in either of the given ranges
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Note: Use `\` to escape special characters (e.g. `\`, `/`, `[`, `]`, `(`, `)`, `{`, `}` etc.).
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### Quantifiers
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- `a?`: zero or one of `a` (equal to `a{0,1}`)
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- `a*`: zero or more of `a` (equal to `a{0,}`)
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- `a+`: one or more of `a` (equal to `a{1,}`)
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- `a{3}`: exactly 3 of `a`
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- `a{3,}`: 3 or more of `a`
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- `a{3,5}`: between 3 and 5 of `a` (inclusive)
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Note: `a` is any valid quantifiable expression.
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### Groups
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- `(ab)`: match and capture everything enclosed (here exactly `ab`)
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- `(a|b)`: match and capture either one character (here `a` or `b`)
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- `(?:ab)`: match everything enclosed, without capturing
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### Flags
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- `g`: Global
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- `m`: Multiline
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- `i`: Case insensitive
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- `u`: Unicode
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Note that this cheatsheet is meant only as a starting point and is by no means a complete guide to all the features and nuances of regular expressions. You can also read [6 JavaScript Regular Expression features you can use today](/blog/s/6-javascript-regexp-tricks) for a deeper dive into some more advanced features.
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