gen_next.js

function* addGen(sum){

let first= yield sum;
sum+=first;
  
let second=yield sum;
sum+=second;

return sum;

}
let addwith=addGen(40);

console.log(addwith.next()); //@yields {value: 40, done: false}
console.log(addwith.next(40)); //@yields  {value: 80, done: false}
console.log(addwith.next(20)); //@returns {value: 100, done: true}