Generator和Iterator的关系

 var myIterator = {}
        //Generator函数就是一个遍历器对象的生成函数
        myIterator[Symbol.iterator] = function* () {
            yield 1;
            yield 2;
            yield 3;
        }

        for (let v of myIterator) {
            console.log(v)
        }

        function* gen() {

        }
        //通过Generator函数执行后返回遍历器对象
        let g = gen()
        //遍历器对象本身也具有Symbol.iterator
        console.log(g[Symbol.iterator]() === g)


        function* foo() {
            yield 1;
            yield 2;
            yield 3;
            yield 4;
            return 5;
        }

        for (let v of foo()) {
            console.log(v)
        }