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Javascript in 100 bits

Course by zooboole,

Last Updated on 2025-01-28 08:04:00

Lesson 65 - Character Classes in Regular Expressions

Character classes in regular expressions allow you to match specific sets of characters. They provide a way to define which characters should be matched.

Common Character Classes

Character Class Meaning Example Matches
\d Matches any digit (0-9) /\d+/ "123" in "abc123"
\D Matches any non-digit /\D+/ "abc" in "abc123"
\w Matches any word character (letters, digits, underscore) /\w+/ "hello_123"
\W Matches any non-word character /\W+/ "!", "@#", etc.
\s Matches any whitespace (space, tab, newline) /\s+/ " " in "hello world"
\S Matches any non-whitespace character /\S+/ "hello" in "hello world"

Example 1: Matching Digits

let text = "My age is 25.";
let result = text.match(/\d+/g);
console.log(result); // Output: ["25"]

Example 2: Extracting Words

let text = "Coding is fun!";
let words = text.match(/\w+/g);
console.log(words); // Output: ["Coding", "is", "fun"]

Example 3: Identifying Non-Alphanumeric Characters

let text = "Hello, World!";
let specialChars = text.match(/\W+/g);
console.log(specialChars); // Output: [", ", "!"]

Try Your Hand

Steps:

  1. Create a File:

    • Name it lesson65-character-classes.html.

  2. Write the Code:

    <!DOCTYPE html>
<html lang="en">
<head>
   <meta charset="UTF-8">
   <meta name="viewport" content="width=device-width, initial-scale=1.0">
   <title>Lesson 65 - Character Classes</title>
</head>
<body>
   <h2>Character Classes Demo</h2>
   <p id="output"></p>

   <script>
       let text = "Contact me at info@example.com or call 555-1234.";
       let matches = text.match(/\d+/g); // Extracts numbers

       document.getElementById("output").textContent = "Numbers found: " + matches.join(", ");
   </script>
</body>
</html>

  3. Save the File.

  4. Open it in a Browser to See Extracted Numbers.

Experiment

  1. Extract all words from a given sentence.
  2. Find all non-word characters in a string.
  3. Identify whitespace characters in a text.

Key Takeaways

  • Character classes provide powerful shortcuts for matching groups of characters.
  • \d, \w, \s, and their uppercase versions have opposite meanings.
  • Useful for validations and text processing.