What is Regex | Regular Expression 🪄
Regular expressions (regex) are patterns used to match and manipulate strings. Here are some key concepts:
Basic Concepts
1. *Patterns*: Regex patterns are used to match strings.
2. *Literal characters*: Most characters match themselves (e.g., "a" matches "a").
3. *Special characters*: Some characters have special meanings (e.g., "." matches any character).
Common Regex Patterns
1. *.*: Matches any single character.
2. *\w*: Matches word characters (letters, digits, or underscores).
3. *\W*: Matches non-word characters.
4. *\d*: Matches digits.
5. *\D*: Matches non-digits.
6. *\s*: Matches whitespace characters.
7. *\S*: Matches non-whitespace characters.
Quantifiers
1. ***: Matches 0 or more occurrences.
2. *+*: Matches 1 or more occurrences.
3. *?*: Matches 0 or 1 occurrence.
4. *{n}*: Matches exactly n occurrences.
5. *{n,}*: Matches n or more occurrences.
6. *{n,m}*: Matches between n and m occurrences.
Anchors
1. *^*: Matches the start of a string.
2. *$*: Matches the end of a string.
Groups and Capturing
1. *()*: Groups patterns and captures matches.
2. *\1*, *\2*, etc.: References captured groups.
Regex Methods
1. *test()*: Tests if a string matches a regex pattern.
2. *exec()*: Executes a regex pattern on a string and returns matches.
3. *match()*: Returns an array of matches.
4. *replace()*: Replaces matches with a replacement string.
Example
const regex = /\d+/g;
const string = "Hello123World456";
const matches = string.match(regex);
console.log(matches); // Output: ["123", "456"]
Use Cases
1. *Validation*: Validate user input (e.g., email addresses, phone numbers).
2. *Extraction*: Extract data from strings (e.g., parsing log files).
3. *Replacement*: Replace substrings in strings.
By mastering regex, you can efficiently work with strings and perform complex text processing tasks.
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