Regular Expression (Regex or RegExp for short) is a powerful tool for matching text patterns. Some examples of commonly used regular expression patterns include:
1. Match numbers:
Match integers: \d+
Match floating point numbers: \d+.\d+
2. Match letters and numbers: \w+
3. Match whitespace characters:
Space: (a space character)
Tab: \tNewline
: \n
4. Match specific characters:
Matches letters: [a-zA-Z]
Matches numbers: [0-9]
Matches non-alphanumeric characters: [^a-zA-Z0-9]
Matches a specific set of characters: [aeiou] (matches vowels)
5. Match duplicates:
Match one or more characters: +
Match zero or more characters: *
Match zero or one character: ?
Match a fixed number of characters: {n} (for example, \d{3} matches three consecutive digits)
6. Anchor the beginning and end of the string:
Matches the beginning of a string: ^
Matches the end of a string: $
7. Grouping and capturing:
Use parentheses to group: (pattern)
Capture grouping: ([az]+)
8. Escape characters:
Escape special characters: \ (for example, . matches the period character)
9. Or operation: | (for example, cat|dog matches "cat" or "dog")
10. Ignore case: /i flag (for example, /pattern/i matches case-insensitively)
These are common regular expression patterns, but the regular expression syntax is very rich and can be customized to your specific needs and matching requirements. Regular expressions are very useful in text processing, data extraction, validating input, etc. However, please note that regular expressions can also be very complex and difficult to understand and maintain, so they need to be used with caution.