function* yield

function* gen() {

var result1 = yield "hello";

var result2 = yield "world";

return result1 + result2;

}

var g = gen();

// g.next(1);

//{value : 'hello', done : false}

// g.next(2);

//{value : 'world', done : false}

// g.next();

//{value : 3, done: true}

// g.next();

//{value : undefined, done: true}

console. log( g. next( 1));