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Regular Expression Tester

Regular Expression Tester

Output:

A) Regular Expression Rules

Welcome to the Regular Expression Tester Tool! This tool helps you test and validate regular expressions against your input strings. Follow this guide to learn how to use the tool effectively.

Expression Description Example
^ Matches the start of a string. ^Hello matches "Hello" in "Hello World".
$ Matches the end of a string. World$ matches "World" in "Hello World".
. Matches any single character except newline. a.c matches "abc", "adc", but not "ac".
* Matches 0 or more occurrences of the preceding element. ab* matches "a", "ab", or "abbb".
+ Matches 1 or more occurrences of the preceding element. ab+ matches "ab", "abb", but not "a".
? Matches 0 or 1 occurrence of the preceding element. ab? matches "a" or "ab".
{n} Matches exactly n occurrences of the preceding element. a{3} matches "aaa".
{n,} Matches n or more occurrences of the preceding element. a{2,} matches "aa", "aaa", and so on.
{n,m} Matches between n and m occurrences of the preceding element. a{1,3} matches "a", "aa", or "aaa".
[abc] Matches any character in the brackets. [abc] matches "a", "b", or "c".
[^abc] Matches any character not in the brackets. [^abc] matches "d" but not "a", "b", or "c".
(xyz) Captures and groups the characters xyz. (abc)+ matches "abc", "abcabc", etc.
| Acts as an OR operator between expressions. cat|dog matches "cat" or "dog".
\d Matches any digit (0-9). \d+ matches "123", "456", etc.
\D Matches any non-digit character. \D+ matches "abc", "XYZ", etc.
\w Matches any word character (alphanumeric or underscore). \w+ matches "hello123", "word_", etc.
\W Matches any non-word character. \W+ matches "!", "@#$", etc.
\s Matches any whitespace character. \s+ matches spaces, tabs, etc.
\S Matches any non-whitespace character. \S+ matches "hello", "world", etc.
\b Matches a word boundary. \bcat\b matches "cat" but not "scatter".
\B Matches a non-word boundary. \Bcat\B matches "scatter" but not "cat".

B) Features

  • Test regular expressions against single-line or multiline input.
  • Supports flags for case-insensitivity and multiline matching.
  • Displays matched results or error messages if the regex is invalid.
  • User-friendly interface with a dark theme.

C) How to Use the Tool

1. Access the Tool

Simply open the tool in a web browser. The tool is lightweight and works in any modern browser without requiring additional plugins.

2. Input Regular Expression

  • Locate the "Enter Regular Expression" field.
  • Type your regular expression here (e.g., ^[A-Z]+\d+$).
  • The tool accepts valid JavaScript regex syntax.

3. Input Test String

  • Locate the "Enter Test String" textarea.
  • Type or paste the string you want to test the regex against. You can include multiple lines of text if necessary.
  • Example:
ABC123
DEF456
GHI789

4. Test the Regular Expression

  • Click the "Test Regex" button.
  • The tool will evaluate the regular expression against the test string.

5. View Results

  • If matches are found, they will be displayed in the Output section as a list.
  • Example Output:
    • Matches Found:
ABC123
DEF456
GHI789
  • If no matches are found, you will see "No matches found."
  • If the regular expression is invalid, an error message will appear in red.

D) Example Usage

Example 1: Single-Line Matching

  • Regular Expression:^[A-Z]+\d+$
  • Test String:ABC123
  • Expected Output:
Matches Found:
ABC123


Example 2: Multiline Matching

  • Regular Expression:^[A-Z]+\d+$
  • Test String:
ABC123
DEF456
GHI789

Expected Output:

Matches Found:
ABC123
DEF456
GHI789


Example 3: Case-Insensitive Matching

  • Regular Expression:^[a-z]+\d+$
  • Flags: Add i for case-insensitivity.
  • Test String:abc123
  • Expected Output:
Matches Found:
abc123

E) Tips for Effective Use

  • Use the ^ and $ anchors to match the beginning and end of lines.
  • Add the g flag to find all matches in the string.
  • Use the m flag to enable multiline mode.
  • Escape special characters like . or * with a backslash (e.g., \., \*).

F) Troubleshooting

Error: No Matches Found

  • Ensure your regex is correct and matches the input string.
  • Check if you need to use additional flags like i or m.

Error: Invalid Regular Expression

  • Review your regex for syntax errors.
  • Use tools or resources like MDN Regex Reference for guidance.

G) Support

For further assistance or feedback, please contact us at rustcode95@gmail.com.

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