其他

异步加法

参考 https://juejin.cn/post/7134583899597832200?share_token=f60dd2f4-aab2-4adb-aaef-83209f3d608a

function asyncAdd(a, b, cb) {
  setTimeout(() => {
    cb(null, a + b);
  }, Math.random() * 1000);
}

async function total() {
  const res1 = await sum(1, 2, 3, 4, 5, 6, 4);
  const res2 = await sum(1, 2, 3, 4, 5, 6, 4);
  return [res1, res2];
}

total();

// 实现下 sum 函数。注意不能使用加法，在 sum 中借助 asyncAdd 完成加法。尽可能的优化这个方法的时间。
const cash: any = {};

function isUndefined(target: any) {
  return target === void 0;
}

async function sum(...nums: number[]) {
  let res: any = 0;
  const key = nums.join("+");

  if (!isUndefined(cash[key])) return cash[key];

  for (const n of nums) {
    res = await caculate(res, n);
  }
  cash[key] = res;
  return res;
}

function caculate(num1: number, num2: number) {
  return new Promise((resolve, reject) => {
    asyncAdd(num1, num2, (err: any, rs: number) => {
      if (err) {
        reject(err);
        return;
      }
      resolve(rs);
    });
  });
}

如何进一步优化？

• Promise.all，并行计算

版本号排序

有一组版本号如下['0.1.1', '2.3.3', '0.302.1', '4.2', '4.3.5', '4.3.4.5']。 现在需要对其进行排序，排序的结果为 ['4.3.5','4.3.4.5','2.3.3','0.302.1','0.1.1']

arr.sort((a, b) => {
  let i = 0;
  const arr1 = a.split(".");
  const arr2 = b.split(".");
  while (true) {
    const s1 = arr1[i];
    const s2 = arr2[i];
    i++;
    if (s1 === undefined || s2 === undefined) {
      return arr2.length - arr1.length;
    }
    if (s1 === s2) continue;
    return s2 - s1;
  }
});
console.log(arr);

参考 https://github.com/hengg/js-walker/issues/9

LazyMan

实现一个 LazyMan，可以按照以下方式调用:

LazyMan(“Hank”)
// 输出
Hi! This is Hank!

LazyMan(“Hank”).sleep(10).eat(“dinner”)
// 输出
Hi! This is Hank!
// 等待10秒
Wake up after 10
Eat dinner~

LazyMan(“Hank”).eat(“dinner”).eat(“supper”)
// 输出
Hi This is Hank!
Eat dinner~
Eat supper~

LazyMan(“Hank”).eat(“supper”).sleepFirst(5)
// 输出
// 等待5秒
Wake up after 5
Hi This is Hank!
Eat supper

class _LazyMan {
  constructor(name) {
    this.taskQueue = [];
    this.name = name;
    this.timer = null;
    this.sayHi();
  }
  next() {
    clearTimeout(this.timer);
    this.timer = setTimeout(async () => {
      for (let i = 0; i < this.taskQueue.length; i++) {
        await this.taskQueue[i]();
      }
    });
    return this;
  }
  sayHi() {
    this.taskQueue.push(() => {
      console.log("Hi! This is " + this.name);
    });
    return this.next();
  }
  eat(str) {
    this.taskQueue.push(() => {
      console.log("Eat " + str);
    });
    return this.next();
  }
  beforSleep(time) {
    this.taskQueue.unshift(() => this.sleepPromise(time));
    return this.next();
  }
  sleep(time) {
    this.taskQueue.push(() => this.sleepPromise(time));
    return this.next();
  }
  sleepPromise(time) {
    return new Promise((resolve, reject) => {
      setTimeout(() => {
        console.log("wake up after " + time);
        resolve();
      }, time * 1000);
    });
  }
}

function LazyMan(name) {
  return new _LazyMan(name);
}

LazyMan("Hank");
LazyMan("Hank").sleep(10).eat("dinner");