gen_yield.js

let yielder=function*(){
 yield yield yield 'first';
}
let race=yielder();
console.log(race.next());         //@yields {value: "first", done: false}
console.log(race.next('second')); //@yields {value: "second", done: false}
console.log(race.next('third'));  //@yields {value: "third", done: false}