JAVASCRIPT

default in javascript

const greet = (message = 'Hello World!') => console.log(message);

greet(); // prints 'Hello World!'
greet('Hello! Does this answer your question?') // prints 'Hello! Does this answer your question?'

.default in javascript

function multiply(a, b) {
  b = (typeof b !== 'undefined') ?  b : 1
  return a * b
}

multiply(5, 2)  // 10
multiply(5)     // 5

default javascript

function say(message='Hi') {
    console.log(message);
}

say(); // 'Hi'
say('Hello') // 'Hello'