如何使用Promise完成以下需求

Question

f2和f3依赖于f1的结果，f4依赖于f2和f3的结果，f6依赖于f3和f4和f5的结果？怎么写效率最高？    f1   /    \f2      f3      f5  \    / \     /    f4    \   /       \   \ /           f6

Answer 1

f1().then(data1 => promise.all([f2(data1), f3(data1)]))

    .then(([data2, data3]) => promsie.all([f4({ data2, data3 }), f5()])

    .then(([data4, data5]) => f6({ data3, data4, data5 })))

    .then(data6 => console.log('结束'))

Answer 2

            let temp = f1().then(data1 => {

                return Promise.all([f2(), f3()])

            }).then(([data2, data3]) => {

                return Promise.all([f4(), Promise.resolve(data3)])

            })

            Promise.all([temp, f5()]).then(([[data4, data3], data5]) => {

                console.log(data4, data3, data5)

                return f6()

            }).catch(error=>{

                console.log(error)

            })

Answer 3

f5没有依赖，所以f5执行的越早越有利，尤其是f5响应时间>f4的时候

// 模拟下请求

const timeConsumingFunc = param=>new Promise(

  (resolve) => {

    let timeout = Math.random() * 5000;

    console.log(`task ${param} will be resolved in ${timeout}ms`);

    setTimeout(() => {

      console.log(`${param} resolved`);

      resolve(param+10);

    }, timeout);

  }

);

console.time('totalTime2');

Promise.all([(()=>{

  return timeConsumingFunc(1).then(res1 => {

    console.log(`f1 get response: ${res1}`);

    return Promise.all([timeConsumingFunc(2),timeConsumingFunc(3)]);

  }).then(([res2,res3])=>{

    console.log(`f2 get response: ${res2}`);

    console.log(`f3 get response: ${res3}`);

    return timeConsumingFunc(4);

  });

})(),timeConsumingFunc(5)]).then(([res4,res5])=>{

  console.log(`f4 get response: ${res4}`);

  console.log(`f5 get response: ${res5}`);

  return timeConsumingFunc(6);

}).then(res6=>{

  console.log(`f6 get response: ${res6}`);

  console.timeEnd('totalTime2');

});

最终时间大致=MAX{(f1 + MAX(f2,f3) + f4), f5} + f6