JavaScript Strings and String Methods

A string is a sequence of characters used to represent text. Strings are one of the most frequently used data types in JavaScript — everything from a person's name to a full web page address is stored as a string.

JavaScript provides a rich set of built-in string methods to manipulate, search, and format text efficiently.

Creating Strings

Strings can be created using single quotes, double quotes, or backticks (template literals).

let name1 = 'Ananya';           // Single quotes
let name2 = "Rajan";            // Double quotes
let greeting = `Hello, World!`; // Backticks (Template literal)

All three work the same way. Backticks are the modern choice because they support embedded expressions.

String Length

let text = "JavaScript";
console.log(text.length);  // 10

Accessing Characters

Individual characters in a string are accessed using their index (starting from 0).

let word = "Hello";
console.log(word[0]);  // H
console.log(word[4]);  // o

// charAt() method
console.log(word.charAt(1));  // e

String Concatenation

Strings are joined using the + operator or the concat() method.

let firstName = "Vikas";
let lastName = "Sharma";
let fullName = firstName + " " + lastName;
console.log(fullName);  // Vikas Sharma

// Using concat()
let result = firstName.concat(" ", lastName);
console.log(result);  // Vikas Sharma

Template Literals (ES6)

Template literals use backticks and allow embedding variables directly into strings using ${ }. This is much cleaner than string concatenation.

let product = "Laptop";
let price = 55000;

console.log(`The ${product} costs ₹${price}.`);
// Output: The Laptop costs ₹55000.

Multi-line Strings with Template Literals

let message = `Dear Customer,

Thank you for your order.
Your item will be delivered within 3 days.

Regards,
Support Team`;

console.log(message);

Case Conversion Methods

toUpperCase() — Convert to Uppercase

let text = "hello world";
console.log(text.toUpperCase());  // HELLO WORLD

toLowerCase() — Convert to Lowercase

let text = "JAVASCRIPT IS FUN";
console.log(text.toLowerCase());  // javascript is fun

Removing Whitespace

trim() — Remove Spaces from Both Ends

let input = "   hello   ";
console.log(input.trim());         // "hello"
console.log(input.trimStart());    // "hello   "
console.log(input.trimEnd());      // "   hello"

Searching in Strings

includes() — Check if a Substring Exists

let sentence = "JavaScript is a popular language";
console.log(sentence.includes("popular"));  // true
console.log(sentence.includes("Python"));   // false

startsWith() and endsWith()

let url = "https://estudy247.com";
console.log(url.startsWith("https"));  // true
console.log(url.endsWith(".com"));     // true

indexOf() — Find Position of a Substring

let text = "Learn JavaScript with us";
console.log(text.indexOf("JavaScript"));  // 6
console.log(text.indexOf("Python"));      // -1 (not found)

lastIndexOf() — Find Last Occurrence

let text = "apple mango apple banana apple";
console.log(text.lastIndexOf("apple"));  // 19 (position of last occurrence)

Extracting Substrings

slice(start, end) — Extract Part of a String

let text = "JavaScript Tutorial";
console.log(text.slice(0, 10));   // JavaScript
console.log(text.slice(11));      // Tutorial
console.log(text.slice(-8));      // Tutorial (negative index from end)

substring(start, end) — Similar to slice but No Negative Index

let text = "Hello World";
console.log(text.substring(6, 11));  // World

Replacing Content

replace() — Replace First Occurrence

let text = "I love cats. Cats are cute.";
console.log(text.replace("cats", "dogs"));  // I love dogs. Cats are cute.

replaceAll() — Replace All Occurrences

let text = "apple, apple, apple";
console.log(text.replaceAll("apple", "mango"));  // mango, mango, mango

Splitting a String

split() — Convert String to Array

let fruits = "Apple,Banana,Mango,Orange";
let fruitArray = fruits.split(",");
console.log(fruitArray);  // ["Apple", "Banana", "Mango", "Orange"]

// Split by space
let sentence = "Hello World JavaScript";
console.log(sentence.split(" "));  // ["Hello", "World", "JavaScript"]

// Split each character
console.log("abc".split(""));  // ["a", "b", "c"]

Padding Strings

padStart() and padEnd() — Add Padding to Reach a Target Length

// Useful for formatting invoice numbers, times, etc.
let id = "42";
console.log(id.padStart(5, "0"));  // "00042"

let amount = "500";
console.log(amount.padEnd(8, "."));  // "500....."

Repeating Strings

let star = "*";
console.log(star.repeat(5));  // *****

String to Number and Back

// String to Number
let strNum = "42";
console.log(Number(strNum));      // 42
console.log(parseInt(strNum));    // 42

// Number to String
let num = 100;
console.log(num.toString());      // "100"
console.log(String(num));         // "100"

Escape Characters

Special characters inside strings are represented using backslash \ escape sequences.

let message = "He said, \"Hello!\"";
console.log(message);  // He said, "Hello!"

let lines = "Line 1\nLine 2\nLine 3";
console.log(lines);
// Line 1
// Line 2
// Line 3

Practical Example — Format a User Profile

let rawName = "  ananya sharma  ";
let email = "ANANYA@EXAMPLE.COM";
let phone = "9876543210";

let cleanName = rawName.trim();
let formattedName = cleanName
  .split(" ")
  .map(word => word[0].toUpperCase() + word.slice(1).toLowerCase())
  .join(" ");

let formattedEmail = email.toLowerCase();
let formattedPhone = phone.slice(0, 5) + "-" + phone.slice(5);

console.log("Name:", formattedName);   // Ananya Sharma
console.log("Email:", formattedEmail); // ananya@example.com
console.log("Phone:", formattedPhone); // 98765-43210

Key Points to Remember

• Strings can use single quotes, double quotes, or backticks
• Template literals (backticks) allow embedding variables with ${ }
• Use trim() to clean up whitespace from user inputs
• toUpperCase() and toLowerCase() change letter casing
• includes(), startsWith(), and endsWith() search within strings
• slice() extracts a portion of a string without modifying the original
• replace() and replaceAll() substitute text within strings
• split() converts a string into an array
• Strings are immutable — methods always return a new string, never modify the original