第 14 题：简单实现async/await中的async函数

[airuikun]

async 函数的实现原理，就是将 Generator 函数和自动执行器，包装在一个函数里

function spawn(genF) {
    return new Promise(function(resolve, reject) {
        const gen = genF();
        function step(nextF) {
            let next;
            try {
                next = nextF();
            } catch (e) {
                return reject(e);
            }
            if (next.done) {
                return resolve(next.value);
            }
            Promise.resolve(next.value).then(
                function(v) {
                    step(function() {
                        return gen.next(v);
                    });
                },
                function(e) {
                    step(function() {
                        return gen.throw(e);
                    });
                }
            );
        }
        step(function() {
            return gen.next(undefined);
        });
    });
}

[zheeeng]

同样的效果

function spawn(genF) {
    return new Promise(function(resolve, reject) {
        const gen = genF()
        try {
            while (true) {
                const next = gen.next()
                if (!next.done) continue
                
                resolve(next.value)
                break
            }
        } catch (e) {
            return reject(e);
        }
    })
}

这是不是简单多了
谬，理解错题意了

function spawn(genF) {
    const gen = genF()

    return function next (v) {
        return new Promise((resolve, reject) => {
            try {
                const result = gen.next(v)
                if (result.done) {
                    return resolve(result.value)
                }

                return Promise.resolve(result.value).then(next).then(resolve, reject)
            } catch (e) {
                reject(e)
            }
        })
    } ()
}