YouTipRegexp Tutorial
# Regular Expressions - Tutorial
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A Regular Expression (Regex or RegExp for short) is a pattern used to match character combinations in strings.
Regular expressions are a tool for pattern matching and searching text.
Regular expressions provide a flexible and powerful way to find, replace, validate, and extract text data.
Regular expressions can be applied in various programming languages and text processing tools, such as JavaScript, Python, Java, Perl, etc.
Introductory video: (https://mp.weixin.qq.com/s/TIub-jz9KU2ngoDg5FCnDQ).
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## What Can Regular Expressions Do?
* **Find:** Locate specific patterns within text.
* **Replace:** Substitute text that matches a certain pattern with other content.
* **Validate:** Check if input data conforms to an expected format.
* **Extract:** Extract needed information from complex text.
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## Example
The following example finds numbers in the string `str`:
## Example
Extract the numeric part from the string `str` (match once):
```javascript
var str = "abc123def";
var patt1 = /+/;
document.write(str.match(patt1));
The marked text is the matched expression:
123
[Try it »](#)
### Test Tool
Flags:
__**+**
Matching text:
abc_123_def
## Regular Expression Patterns
Regular expression patterns can include the following:
* Literal characters: For example, letters, numbers, spaces, etc., which can match themselves directly.
* Special characters: For example, the dot `.`, asterisk `*`, plus `+`, question mark `?`, etc., which have special meanings and functions.
* Character classes: A set of characters enclosed in square brackets ``, used to match any single character within the brackets.
* Metacharacters: For example, `d`, `w`, `s`, etc., used to match specific types of characters, such as digits, letters, whitespace characters, etc.
* Quantifiers: For example, `{n}`, `{n,}`, `{n,m}`, etc., used to specify the number or range of matches.
* Boundary markers: For example, `^`, `$`, `b`, `B`, etc., used to match the start, end, or word boundary positions of a string.
## Content List
* ( "Regular Expressions Online Test")
* ( "Regular Expressions - Visualization Tool")
### Other Related Tools
* [AI Regex Analysis Tool!](https://www.jyshare.com/front-end/9064/)
* [RegExr -- Regular Expressions Online Testing Tool.](https://regexr.com/)
* [Regulex -- Regular Expressions Online Testing Tool.](https://regex101.com/)