JavaScript String

In JavaScript, strings are used to represent and manipulate a sequence of characters. Strings are immutable, meaning once they are created, their content cannot be changed.

Creating Strings

1. Using Double Quotes

const string1 = “Hello, World!”;

2. Using Single Quotes

const string2 = ‘Hello, World!’;

Common String Methods

1. length Property: Returns the length of the string.

const str = “Hello, World!”;

console.log(str.length); // Output: 13

2. charAt(index): Returns the character at the specified index.

const str = “Hello, World!”;

console.log(str.charAt(0)); // Output: H

3. indexOf(searchValue): Returns the index of the first occurrence of the specified value, or -1 if not found.

const str = “Hello, World!”;

console.log(str.indexOf(“World”)); // Output: 7

console.log(str.indexOf(“world”)); // Output: -1

4. lastIndexOf(searchValue): Returns the index of the last occurrence of the specified value, or -1 if not found.

const str = “Hello, World! Hello!”;

console.log(str.lastIndexOf(“Hello”)); // Output: 14

5. includes(searchValue): Returns true if the string contains the specified value, otherwise false.

const str = “Hello, World!”;

console.log(str.includes(“World”)); // Output: true

console.log(str.includes(“world”)); // Output: false

6. startsWith(searchValue): Returns true if the string starts with the specified value, otherwise false.

const str = “Hello, World!”;

console.log(str.startsWith(“Hello”)); // Output: true

console.log(str.startsWith(“World”)); // Output: false

7. endsWith(searchValue): Returns true if the string ends with the specified value, otherwise false.

const str = “Hello, World!”;

console.log(str.endsWith(“World!”)); // Output: true

console.log(str.endsWith(“Hello”)); // Output: false

8. substring(start, end): Returns the part of the string between the start and end indexes.

const str = “Hello, World!”;

console.log(str.substring(0, 5)); // Output: Hello

9. slice(start, end): Similar to substring but also supports negative indices.

const str = “Hello, World!”;

console.log(str.slice(0, 5)); // Output: Hello

console.log(str.slice(-6, -1)); // Output: World

10. toLowerCase(): Returns the string converted to lowercase.

const str = “Hello, World!”;

console.log(str.toLowerCase()); // Output: hello, world!

11. toUpperCase(): Returns the string converted to uppercase.

const str = “Hello, World!”;

console.log(str.toUpperCase()); // Output: HELLO, WORLD!

12. trim(): Removes whitespace from both ends of the string.

const str = ” Hello, World! “;

console.log(str.trim()); // Output: Hello, World!

13. replace(searchValue, replaceValue): Returns a new string with some or all matches of a pattern replaced by a replacement.

const str = “Hello, World!”;

const newStr = str.replace(“World”, “Universe”);

console.log(newStr); // Output: Hello, Universe!

14. split(separator): Splits a string into an array of substrings using the specified separator.

const str = “Hello, World!”;

const arr = str.split(“, “);

console.log(arr); // Output: [“Hello”, “World!”]