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articles/snippets/common-regexp-cheatsheet.md

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+---
+title: Common regular expressions
+type: cheatsheet
+tags: [javascript,string,regexp]
+author: chalarangelo
+cover: rocky-beach
+excerpt: A collection of regular expressions that can be used to solve common problems.
+dateModified: 2022-11-09T05:00:00-04:00
+---
+
+### Exact string match
+
+- Use the `^` and `$` anchors to match the start and end of the string, respectively.
+- Add the string you want to match in-between the two anchors.
+
+```js
+const regexp = /^abc$/;
+// Where 'abc' is the exact string you want to match
+```
+
+### Match empty string
+
+- Use the `^` and `$` anchors to match the start and end of the string, respectively.
+- Do not add any characters in-between to match an empty string.
+
+```js
+const regexp = /^$/;
+```
+
+### Match whitespace sequences
+
+- Use the `\s` meta-sequence to match any whitespace character, including spaces, tabs, newlines, etc.
+- Use the `+` quantifier to match one or more occurrences of the previous character.
+- Add the global flag (`g`) to match all occurrences of the pattern in the string.
+
+```js
+const regexp = /\s+/g;
+```
+
+### Match line breaks
+
+- Depending on the environment, line breaks can be represented in different ways.
+- Use the `\r` character to match carriage returns, the `\n` character to match newlines, and the `\r\n` sequence to match carriage returns followed by newlines.
+- Add the global (`g`) and multiline (`m`) flags to match all occurrences of the pattern in the string.
+
+```js
+const regexp = /\r|\n|\r\n/gm;
+```
+
+### Match non-word characters
+
+- Use negation (`^`) to match any character that is not a word character (`\w`) or a whitespace character (`\s`).
+- Add the global flag (`g`) to match all occurrences of the pattern in the string.
+- Add the ignore case flag (`i`) to match both uppercase and lowercase characters.
+
+```js
+const regexp = /[^\w\s]/gi;
+```
+
+### Match alphanumeric, dashes and hyphens
+
+- Use the `^` and `$` anchors to match the start and end of the string, respectively.
+- Use the `a-zA-Z0-9-` pattern to match any alphanumeric character, dashes and hyphens.
+- Use the `+` quantifier to match one or more occurrences of the previous character.
+- Particularly useful when matching URL slugs.
+
+```js
+const regexp = /^[a-zA-Z0-9-_]+$/;
+```
+
+### Match letters and whitespaces
+
+- Use the `^` and `$` anchors to match the start and end of the string, respectively.
+- Use the `a-zA-Z\s` pattern to match any letter and whitespace character.
+- Use the `+` quantifier to match one or more occurrences of the previous pattern.
+
+```js
+const regexp = /^[A-Za-z\s]+$/;
+```
+
+### Pattern not included
+
+- Use the `^` and `$` anchors to match the start and end of the string, respectively.
+- Use a negative lookahead (`?!`) to match any character that is not followed by the pattern you want to exclude.
+- Add the global flag (`g`) to match all occurrences of the pattern in the string.
+- To ensure more than one pattern is not included, use the `|` character to separate them.
+
+```js
+const regexp = /^((?!(abc|bcd)).)*$/;
+// Where 'abc' and 'bcd' are pattern you want to exclude
+```
+
+### Text inside brackets
+
+- Use the `\(` and `\)` characters to match the opening and closing brackets, respectively.
+- Use a capturing group between the two and exclude the closing parenthesis character.
+- Use the `+` quantifier to match one or more characters, as needed.
+- Add the global flag (`g`) to match all occurrences of the pattern in the string.
+- Replace `\(` and `\)` with `\[` and `\]` to match square brackets and with `\{` and `\}` to match curly brackets.
+
+```js
+const regexp = /\(([^)]+)\)/g;
+```
+
+### Validate GUID/UUID
+
+- Use the `^` and `$` anchors to match the start and end of the string, respectively.
+- Validate each segment of the GUID/UUID separately using numeric character ranges and quantifiers.
+
+```js
+const regexp = /^(0?[1-9]|[12][0-9]|3[01])[\/\-](0?[1-9]|1[012])[\/\-]\d{4}$/;
+```
+
+### Validate date format (DD/MM/YYYY)
+
+- Use the `^` and `$` anchors to match the start and end of the string, respectively.
+- Validate each segment of the date separately using numeric character ranges and quantifiers.
+- Alter the order of the segments and separators to match different formats.
+
+```js
+const regexp = /^(0?[1-9]|[12][0-9]|3[01])[\/\-](0?[1-9]|1[012])[\/\-]\d{4}$/;
+```
+
+### Chunk string into n-size chunks
+
+- Use the `.{1,n}` quantifier to match any character between `1` and `n` times.
+- Add the global flag (`g`) to match all occurrences of the pattern in the string.
+
+```js
+const regexp = /.{1,2}/g;
+// Where '2' is the number of characters per chunk
+```