gen_nested.js

let childgen=function*(){
    yield 'child 1';
    yield 'child 2';
    
    return 'child 3';
}

let parentgen=function*(){

    yield 'parent 1';
    yield 'parent 2';

    let lastchild=yield* childgen();
    return lastchild;
}

let ancestry=parentgen();

console.log(ancestry.next()); //@yields {value: "parent 1", done: false}
console.log(ancestry.next()); //@yields {value: "parent 2", done: false}
console.log(ancestry.next()); //@yields {value: "child 1", done: false}
console.log(ancestry.next()); //@yields {value: "child 2", done: false}
console.log(ancestry.next()); //@returns {value: "child 3", done: true}