JavaScript Regular Expressions

Regular expressions (regex) in JavaScript are patterns used to match character combinations in strings. They provide a powerful and flexible way to search, replace, and validate strings. Here are some common operations and examples of using regular expressions in JavaScript:

1. Matching a specific pattern:

let str = "Hello, World!";
let pattern = /World/;
console.log(pattern.test(str)); // Output: true

2. Matching any character:

let str = "apple";
let pattern = /./; // Matches any single character
console.log(pattern.test(str)); // Output: true

3. Matching a character set:

let str = "hello";
let pattern = /[aeiou]/; // Matches any vowel
console.log(pattern.test(str)); // Output: true

4. Matching repetitions:

let str = "12345";
let pattern = /\d{3}/; // Matches three digits
console.log(pattern.test(str)); // Output: true

5. Matching word boundaries:

let str = "Hello world";
let pattern = /\bHello\b/; // Matches "Hello" only if it's a whole word
console.log(pattern.test(str)); // Output: true

6. Replacing text:

let str = "Hello, world!";
let newStr = str.replace(/world/i, "Universe"); // Case-insensitive replacement
console.log(newStr); // Output: "Hello, Universe!"

7. Splitting strings:

let str = "apple,banana,orange";
let fruits = str.split(/,/); // Split by comma
console.log(fruits); // Output: ["apple", "banana", "orange"]

8. Validating input:

let str = "12345";
let pattern = /^\d{5}$/; // Validates a 5-digit number
console.log(pattern.test(str)); // Output: true

Regular expressions in JavaScript are versatile and can be combined and customized to match a wide range of patterns in strings.

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