JS Regular Expressions

In JavaScript, regular expressions are used to search for and manipulate patterns in strings. Regular expressions are objects that represent a pattern of characters. They are created using the RegExp constructor or using a literal notation, which uses forward slashes (/) to delimit the pattern.

Here are some examples of regular expressions in JavaScript:

				
					// Literal notation
let pattern = /hello/;

// Using RegExp constructor
let pattern = new RegExp("hello");

Regular expressions can be used with several methods on strings, including:

search(): Searches for a match in a string and returns the index of the match.

				
					let str = "hello world";
let pattern = /world/;
let result = str.search(pattern); // returns 6

replace(): Replaces one or more matches in a string with a replacement string.

				
					let str = "hello world";
let pattern = /world/;
let replacement = "JavaScript";
let result = str.replace(pattern, replacement); // returns "hello JavaScript"

match(): Searches for one or more matches in a string and returns an array of the matches.

				
					let str = "hello world";
let pattern = /o/g;
let result = str.match(pattern); // returns ["o", "o"]

Regular expressions can also include special characters, called metacharacters, that have special meanings. Here are some commonly used metacharacters in JavaScript:
. (dot): Matches any character except a newline.
*: Matches zero or more occurrences of the preceding character or group.
+: Matches one or more occurrences of the preceding character or group.
?: Matches zero or one occurrence of the preceding character or group.
[]: Matches any character within the brackets.
^: Matches the beginning of a string.
$: Matches the end of a string.
|: Matches either the pattern before or after the pipe symbol.

Regular expressions can be very powerful, but they can also be complex and difficult to read. It’s important to test and debug regular expressions thoroughly to ensure that they are working as expected.

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JS Regular Expressions

JS Regular Expressions

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