vanilla-generator-math.js

function getTwoPlusTwo() {
    return 2 + 2
}

function* myGeneratorFunction() {
    const sum = yield getTwoPlusTwo()
    console.log("two plus two equals: ", sum)
}

const g = myGeneratorFunction();

console.log("calling next the first time...")
console.log("next: ", g.next())
console.log("calling next the second time...")
console.log("next: ", g.next())

// calling next the first time...
// next:  { value: 4, done: false }
// calling next the second time...
// two plus two equals:  undefined
// next:  { value: undefined, done: true }