generator.js

function *generator() {
  yield 'value1';
  console.log('I am here');
  yield 'value2';
}

const g = generator(); //=> Object [Generator] {}

console.log(g.next()); //=> {value: "value1", done: false}
console.log(g.next()); 
/**
 * I am here
 * {value: "value2", done: false}
**/
console.log(g.next()); //=> {value: undefined, done: true}
console.log(g.next()); //=> {value: undefined, done: true}