Special Characters and Escaping

Special Characters and Escaping

Special Characters in Regex

In Regex, certain characters have special meanings and are used to build complex patterns. These characters include ., ^, $, *, +, ?, \, |, {}, [], (). When you need to match these characters literally, you must escape them with a backslash \.

How to Escape Special Characters

To escape a special character, simply place a backslash before it. For example, to match a literal dot . or a dollar sign $, you use \. and \$ respectively.

	const regexDot = /\./;
	console.log(regexDot.test('example.com')); // true (matches '.')
	
	const regexDollar = /\$/;
	console.log(regexDollar.test('Price: $100')); // true (matches '$')

Example: Matching Special Characters

Let’s see an example that matches a string containing parentheses ():

	const regexParentheses = /\(.*\)/;
	console.log(regexParentheses.test('This is a (test) string.')); // true (matches '(test)')
	
	// Explanation:
	// \(  : Matches the literal '(' character
	// .*  : Matches any character (except newline) 0 or more times
	// \)  : Matches the literal ')' character

Combining Escaped Characters and Metacharacters

You can combine escaped characters with other metacharacters to create more complex patterns. For example, to match a string that starts and ends with parentheses and has any characters in between:

	const regexComplex = /^\(.*\)$/;
	console.log(regexComplex.test('(This is a test)')); // true (matches the entire string)
	console.log(regexComplex.test('This is a (test)')); // false (does not match the entire string)
	
	// Explanation:
	// ^    : Start of the string
	// \(   : Matches the literal '(' character
	// .*   : Matches any character (except newline) 0 or more times
	// \)   : Matches the literal ')' character
	// $    : End of the string

Exercises

1. Write a regular expression that matches a string containing a literal asterisk *.
2. Create a Regex pattern that matches a string containing a literal question mark ? at the end.
3. Write a regular expression that matches a string starting with a literal caret ^ and ending with a literal dollar sign $.

Escaping special characters is essential when you need to include them in your search patterns.