javascript set default undefined code example

Example 1: javascript constructor default parameter

function greet(name, greeting, message = greeting + ' ' + name) {
  return [name, greeting, message]
}

greet('David', 'Hi')                     // ["David", "Hi", "Hi David"]
greet('David', 'Hi', 'Happy Birthday!')  // ["David", "Hi", "Happy Birthday!"]

Example 2: default value of functin atribute

function say(message='Hi', number=7) {
    console.log(message);
  	console.log(number);
}

say();
// 'Hi'
// 7