toLowerCase()

• Description: Converts a string to lowercase letters.

• Example:

  let str = 'Hello, World!';
  console.log(str.toLowerCase()); // Output: 'hello, world!'
  
  

toUpperCase()

• Description: Converts a string to uppercase letters.

• Example:

  let str = 'Hello, World!';
  console.log(str.toUpperCase()); // Output: 'HELLO, WORLD!'