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snippets/js/s/regexp-cheatsheet.md

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+---
+title: Regular Expressions Cheat Sheet
+type: cheatsheet
+language: javascript
+tags: [string,regexp,cheatsheet]
+author: chalarangelo
+cover: tools
+excerpt: Regular expressions are a very useful tool. Save this cheatsheet for when you need to look up their syntax and speed up your development.
+dateModified: 2021-06-12T19:30:41+03:00
+---
+
+### Anchors
+
+- `^`: start of the string or the start of a line in a multiline pattern
+- `$`: end of the string or the end of a line in a multiline pattern
+- `\b`: word boundary
+- `\B`: not word boundary (opposite of `\b`)
+
+Note: Anchors are non-quantifiable (i.e. cannot be followed by a quantifier).
+
+### Character sequences
+
+- `.`: any character except line breaks
+- `\w`: any word character
+- `\W`: any non-word character (opposite of `\w`)
+- `\s`: any whitespace character
+- `\S`: any non-whitespace character (opposite of `\s`)
+- `\d`: any digit character
+- `\D`: any non-digit character (opposite of `\d`)
+- `[abc]`: a single character in the given set (here `a`, `b` or `c`)
+- `[^abc]`: a single character not in the given set (opposite of `[abc]`)
+- `[a-z]`: a single character in the given range (here between `a` and `z` inclusive)
+- `[^a-z]`: a single character not in the given range (opposite of `[a-z]`)
+- `[a-zA-Z]`: a single character in either of the given ranges
+
+Note: Use `\` to escape special characters (e.g. `\`, `/`, `[`, `]`, `(`, `)`, `{`, `}` etc.).
+
+### Quantifiers
+
+- `a?`: zero or one of `a` (equal to `a{0,1}`)
+- `a*`: zero or more of `a` (equal to `a{0,}`)
+- `a+`: one or more of `a` (equal to `a{1,}`)
+- `a{3}`: exactly 3 of `a`
+- `a{3,}`: 3 or more of `a`
+- `a{3,5}`: between 3 and 5 of `a` (inclusive)
+
+Note: `a` is any valid quantifiable expression.
+
+### Groups
+
+- `(ab)`: match and capture everything enclosed (here exactly `ab`)
+- `(a|b)`: match and capture either one character (here `a` or `b`)
+- `(?:ab)`: match everything enclosed, without capturing
+
+### Flags
+
+- `g`: Global
+- `m`: Multiline
+- `i`: Case insensitive
+- `u`: Unicode
+
+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.