default in javascript

1const greet = (message = 'Hello World!') => console.log(message);
2
3greet(); // prints 'Hello World!'
4greet('Hello! Does this answer your question?') // prints 'Hello! Does this answer your question?'

1function say(message='Hi') {
2    console.log(message);
3}
4
5say(); // 'Hi'
6say('Hello') // 'Hello'