JavaScript RegExp Methods

Core RegExp Methods

regex.test(string)

regex.exec(string)

regex.toString()

// Don't use

🔹 test() Method

The test() method returns true if the pattern matches:

// Using test() method
let emailRegex = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;

let emails = [
    "[email protected]",
    "invalid-email",
    "[email protected]",
    "not.an.email"
];

console.log("Email validation results:");
emails.forEach(email => {
    let isValid = emailRegex.test(email);
    console.log(`${email}: ${isValid ? 'Valid' : 'Invalid'}`);
});

// Case-insensitive test
let caseRegex = /hello/i;
console.log("\nCase-insensitive test:");
console.log("HELLO:", caseRegex.test("HELLO"));
console.log("hello:", caseRegex.test("hello"));
console.log("Hi there:", caseRegex.test("Hi there"));

🔹 exec() Method

The exec() method returns detailed match information:

// Using exec() method
let regex = /(\w+)\s+(\d+)/g;
let text = "apple 5 banana 3 orange 7";

console.log("Finding word-number pairs:");
let match;
while ((match = regex.exec(text)) !== null) {
    console.log(`Full match: "${match[0]}"`);
    console.log(`Word: "${match[1]}"`);
    console.log(`Number: "${match[2]}"`);
    console.log(`Index: ${match.index}`);
    console.log(`---`);
}

// Single exec() call
let phoneRegex = /(\d{3})-(\d{3})-(\d{4})/;
let phoneText = "Call me at 123-456-7890";
let phoneMatch = phoneRegex.exec(phoneText);

if (phoneMatch) {
    console.log("Phone number found:");
    console.log("Full number:", phoneMatch[0]);
    console.log("Area code:", phoneMatch[1]);
    console.log("Exchange:", phoneMatch[2]);
    console.log("Number:", phoneMatch[3]);
}

🔹 String Methods with RegExp

String methods that work with regular expressions:

// String methods with RegExp
let text = "The quick brown fox jumps over the lazy dog";
let regex = /\b\w{4}\b/g; // 4-letter words

// match() - find all matches
let matches = text.match(regex);
console.log("4-letter words:", matches);

// search() - find first match index
let searchIndex = text.search(/fox/);
console.log("'fox' found at index:", searchIndex);

// replace() - replace matches
let replaced = text.replace(/\b\w{3}\b/g, "***");
console.log("3-letter words replaced:", replaced);

// split() - split by pattern
let words = text.split(/\s+/);
console.log("Word count:", words.length);
console.log("First 3 words:", words.slice(0, 3));

🔹 Advanced Method Usage

Combining methods for complex text processing:

// Text processing with multiple methods
function analyzeText(text) {
    let results = {
        wordCount: 0,
        sentences: 0,
        emails: [],
        phoneNumbers: [],
        urls: []
    };
    
    // Count words
    let wordRegex = /\b\w+\b/g;
    let wordMatches = text.match(wordRegex);
    results.wordCount = wordMatches ? wordMatches.length : 0;
    
    // Count sentences
    let sentenceRegex = /[.!?]+/g;
    let sentenceMatches = text.match(sentenceRegex);
    results.sentences = sentenceMatches ? sentenceMatches.length : 0;
    
    // Find emails
    let emailRegex = /\b[A-Za-z0-9._%+-]+@[A-Za-z0-9.-]+\.[A-Z|a-z]{2,}\b/g;
    results.emails = text.match(emailRegex) || [];
    
    // Find phone numbers
    let phoneRegex = /\b\d{3}-\d{3}-\d{4}\b/g;
    results.phoneNumbers = text.match(phoneRegex) || [];
    
    // Find URLs
    let urlRegex = /https?:\/\/[^\s]+/g;
    results.urls = text.match(urlRegex) || [];
    
    return results;
}

let sampleText = `
Contact us at [email protected] or call 123-456-7890.
Visit our website at https://example.com for more information!
You can also reach support at [email protected].
`;

let analysis = analyzeText(sampleText);
console.log("Text Analysis Results:");
console.log("Words:", analysis.wordCount);
console.log("Sentences:", analysis.sentences);
console.log("Emails:", analysis.emails);
console.log("Phone numbers:", analysis.phoneNumbers);
console.log("URLs:", analysis.urls);