一道蚂蚁金服异步串行面试题 about blogs HOT 4 OPEN

function Helper(val) {
  this.val = val;
}

Helper.prototype.run = function () {
  const next = (i = 0) => {
    if (i === this.val.length) return;
    const fn = this.val[i]();
    fn instanceof Promise
      ? fn.then(next.bind(null, i + 1))
      : next(i + 1);
  }
  next();
}
const createFlow = (arr) => {
  const loop = (innerArr) => {
    let innerFns = [];
    innerArr.forEach((el) => {
      if (Array.isArray(el)) {
        innerFns = innerFns.concat(loop(el));
      } else if (el instanceof Helper) {
        innerFns = innerFns.concat(el.val);
      } else {
        innerFns.push(el);
      }
    })
    return innerFns;
  }

  return new Helper(loop(arr))
}

function Flow(effects = []) {
    this.tasks = effects.reduce((result, effect) => {
        if(effect instanceof Flow) {
            result.push(...effect.tasks);
        } else if(Array.isArray(effect)) {
            result.push(...effect);
        } else {
            result.push(effect);
        }
        return result;
    }, []);
}

Flow.prototype.run = function(callback) {
    return new Promise(async (resolve) => {
        for(let i = 0;i<this.tasks.length;i++) {
           const task = this.tasks[i];
           await task();
        }
        callback();
    });    
}


function createFlow(effects) {
    return new Flow(effects);
}

const log = console.log;

const delay = (ms) => new Promise((resolve) => setTimeout(resolve, ms));

const subFlow = createFlow([() => delay(1000).then(() => log("c"))]);

createFlow([
  () => log("a"),
  () => log("b"),
  subFlow,
  [() => delay(1000).then(() => log("d")), () => log("e")],
]).run(() => {
  console.log("done");
});