function* Generator

function*.js

/*
The function* declaration (function keyword followed by an asterisk) defines a generator function, which returns a Generator object.

You can also define generator functions using the GeneratorFunction constructor and a function* expression.
*/
// Syntax
function* name([param[, param[, ... param]]]) {
   statements
}

// Example
function* anotherGenerator(i) {
  yield i + 1;
  yield i + 2;
  yield i + 3;
}

function* generator(i){
  yield i;
  yield* anotherGenerator(i);
  yield i + 10;
}

var gen = generator(10);

console.log(gen.next().value); // 10
console.log(gen.next().value); // 11
console.log(gen.next().value); // 12
console.log(gen.next().value); // 13
console.log(gen.next().value); // 20