Javascript

// Define the string
var string = 'Hello World!';

// Encode the String
var encodedString = btoa(string);
console.log(encodedString); // Outputs: "SGVsbG8gV29ybGQh"

// Decode the String
var decodedString = atob(encodedString);
console.log(decodedString); // Outputs: "Hello World!"

Python

### encode
import base64
  
sample_string = "Hello World!"
sample_string_bytes = sample_string.encode("ascii")
  
base64_bytes = base64.b64encode(sample_string_bytes)
base64_string = base64_bytes.decode("ascii")
  
print(f"Encoded string: {base64_string}")

### decode
import base64
  
  
base64_string ="SGVsbG8gV29ybGQh"
base64_bytes = base64_string.encode("ascii")
  
sample_string_bytes = base64.b64decode(base64_bytes)
sample_string = sample_string_bytes.decode("ascii")
  
print(f"Decoded string: {sample_string}")