Creating Regular Expressions:

You can create a regular expression using the RegExp constructor or a literal syntax enclosed in slashes (/pattern/).

Using RegExp constructor:

                                      
                                        const regex = new RegExp('pattern');
                                      
                                    

Literal Syntax:

                                      
                                        const regexLiteral = /pattern/;
                                      
                                    

Basic Patterns:

Characters:

A regular expression can consist of literal characters, such as /abc/ to match the sequence "abc."

Quantifiers:

Quantifiers specify how many occurrences of a character or group are expected.

Examples:

• *: Zero or more occurrences
• +: One or more occurrences
• ?: Zero or one occurrence
• {n}: Exactly n occurrences
• {n,}: n or more occurrences
• {n,m}: Between n and m occurrences

Character Classes:

Character classes allow you to match any one of a set of characters.

Square Brackets:

• [abc]: Matches any one of the characters a, b, or c.
• [^abc]: Matches any character except a, b, or c.

Anchors:

Anchors are used to match positions in the string rather than characters.

• ^: Matches the start of a string.
• $: Matches the end of a string.

Modifiers:

i (case-insensitive):

• /pattern/i makes the pattern case-insensitive.

Metacharacters:

\ (backslash):

• Escapes a metacharacter, treating it as a literal character.

Example Usage:

                                          
                                            const text = "Hello, this is a sample text with some patterns.";
const pattern = /pattern/;

console.log(pattern.test(text));  // Output: true
console.log(text.match(pattern)); // Output: ['pattern']                                            
                                          
                                        

Test Regular Expressions Online:

You can test and experiment with regular expressions using online tools like RegExr or Regex101.