Regular Expressions (RegEx) in JavaScript are patterns used to match, search, and replace text. They are powerful tools for validating input, parsing strings, and finding patterns in text.

This blog explains RegEx syntax, methods, and practical examples.

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⭐ 1. Creating Regular Expressions

1. Using Literal Syntax

let pattern = /hello/;
console.log(pattern.test("hello world")); // true

2. Using RegExp Constructor

let pattern = new RegExp("hello");
console.log(pattern.test("hello world")); // true

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⭐ 2. Common RegEx Patterns

Pattern	Description	Example
^	Start of string	/^Hello/
$	End of string	/world$/
.	Any character	/h.llo/
*	0 or more occurrences	/lo*/
+	1 or more occurrences	/lo+/
?	0 or 1 occurrence	/lo?/
\d	Any digit	/\d/
\w	Any word character	/\w/
\s	Any whitespace	/\s/
[...]	Character set	/[aeiou]/

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⭐ 3. RegEx Methods in JavaScript

test()

Checks if a pattern exists in a string.

let pattern = /world/;
console.log(pattern.test("Hello world")); // true

exec()

Returns the matched string or null.

let result = /world/.exec("Hello world");
console.log(result[0]); // world

String.match()

let str = "I love JS";
let matches = str.match(/love/);
console.log(matches[0]); // love

String.replace()

let str = "Hello world";
let newStr = str.replace(/world/, "JavaScript");
console.log(newStr); // Hello JavaScript

String.search()

let str = "Hello world";
console.log(str.search(/world/)); // 6 (index of match)

String.split()

let str = "apple,banana,mango";
let fruits = str.split(/,/);
console.log(fruits); // ["apple","banana","mango"]

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⭐ 4. Practical Example: Email Validation

function validateEmail(email){
  let pattern = /^[^ ]+@[^ ]+\.[a-z]{2,3}$/;
  return pattern.test(email);
}

console.log(validateEmail("test@example.com")); // true
console.log(validateEmail("test@.com"));        // false

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⭐ Conclusion

Regular expressions are powerful and versatile for working with text in JavaScript. They allow developers to validate input, search patterns, and manipulate strings efficiently.

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📌 Citations

🔗 View other articles about Javascript:
https://savanka.com/category/learn/js/

🔗 External Javascript Documentation:
https://www.w3schools.com/js/